I think this class is roughly comparable to the Dwarven Defender, with a lower hit dice and slightly better skills. (It is more group-defense oriented than the DD.) Do you see any balance issues? Thank you. 
Seneschal of Silvera
The most dedicated followers of Silvera can choose to enter a sacred order that has long served as the guardians of holy places. These warders are highly trained in the arts of defense and observation, and learn the special skills needed to protect a fortress. They can be counted upon to defend their position to the death, if necessary, and inflict a great cost on any who would violate their ward.
A seneschal is often a leader among the guards, and in time will rise to the position of captain or commander of the entire company. She may be tasked by her temple with protecting a site that is more difficult to defend, or one that is more frequently subject to assault. If she has the necessary expertise, she may also be called upon to design improved defenses or construct a new fortification.
Most seneschal of silvera are fighters, rangers, clerics, or paladins, as other classes lack the requisite martial training and sophisticated skills needed to defend a fortification.
Hit Die: d10.
Requirements
To qualify to become a seneschal of silvera, a character must fulfill all the following criteria.
Alignment: Lawful Good or Lawful Neutral.
Base Attack Bonus: +5.
Skills: Search 2 ranks.
Feats: Alertness.
Spells: Ability to cast shield other as a divine spell.
Patron: Silvera.
Special: Must have spent at least a full season serving as a guard at an active fortification, such as a city wall or a castle.
Class Skills
The prestige class skills (and the key ability for each skill) are Climb (Str), Craft (Int), Diplomacy (Cha), Heal (Wis), Jump (Str), Knowledge (Engineering), Listen (Wis), Profession (Wis), Ride (Dex), Search (Int), Sense Motive (Wis), Spot (Wis), and Swim (Str).
Skill Points at Each Level: 4 + Int modifier.
Class Features
Weapon and Armor Proficiency: A seneschal of silvera is proficient with all simple and martial weapons, all types of armor, and shields.
Dodge Threat (Ex): A seneschal of silvera is expertly trained in techniques to avoid fatal blows by dodging aside at the last second. Whenever circumstances permit you to retain your Dexterity bonus to AC (if any), you can add your Wisdom modifier as a Dodge bonus to Armor Class when you are threatened by a critical hit. That is, whenever an opponent scores a threat against you, he must roll to hit your AC as adjusted by a positive Wisdom modifier in order to score a critical hit. This Wisdom modifier is cumulative with other Dodge bonuses to AC.
Abjuration Potency (Su): When casting a spell from the school of Abjuration, a seneschal of silvera's class levels are added to the levels of the class used to cast the spell for the purpose of determining the actual class level at which the spell is cast. Thus a character with 7 class levels of cleric and 4 class levels of seneschal of silvera would cast the abjuration spell spell immunity as an 11th-level cleric.
Uncanny Dodge (Ex): At 2nd level a seneschal of silvera retains his Dexterity bonus to AC (if any) even if he is caught flat-footed or struck by an invisible attacker. However, he still loses his Dexterity bonus to AC if immobilized. If a seneschal of silvera already has uncanny dodge from a different class, he automatically gains improved uncanny dodge (see below) instead.
Group Defense (Ex): A seneschal of silvera is highly trained in group defensive tactics. At 3rd level, any allies adjacent to the seneschal can not be flanked. In addition, whenever the seneschal of silvera is using total defense, any adjacent allies gain a +2 bonus to their AC against attacks of opportunity. This bonus stacks with any other AC modifiers.
Delay Advance (Ex): At 3rd level a seneschal is skilled at delaying the advance of an opponent around an exposed flank. The seneschal can attempt to block the movement from an adjacent square to another adjacent square, even if the advance is by means of a 5-ft.-step movement. For purposes of combat, this action is treated as an attack of opportunity, even though it is not triggered by the same conditions. Thus if a seneschal can only perform one attack of opportunity in a round, she can not perform an attack of opportunity in the same round as a delay advance.
The seneschal makes an unarmed melee touch attack against the advancing opponent, which does not trigger an attack of opportunity. If the attack succeeds, a Strength check is made which is opposed by the Defender's Strength or Dexterity check (whichever ability score has the higher modifier.) The bonuses and penalties to this check are identical to those of a Trip attack. If the attack is successful, the opponent is unable to advance and his move action ceases.
Guard's Intuition (Su): At 4th level, a seneschal of silvera developes an intuitive sense of danger while standing guard. When a seneschal of silvera remains awake within a 20-ft.-radius location for at least an hour, she receives a mental alarm each time a creature of Tiny or larger size enters the area or touches it. The alarm remains active until the seneschal departs the area. This is otherwise similar to the alarm spell (caster level equals Hit Dice.)
Improved Uncanny Dodge (Ex): At 5th level, a seneschal of silvera can no longer be flanked. This defense denies a rogue the ability to sneak attack the seneschal of silvera by flanking him, unless the attacker has at least four more rogue levels than the target has seneschal of silvera levels. If a character already has uncanny dodge (see above) from a second class, the character automatically gains improved uncanny dodge instead, and the levels from the classes that grant uncanny dodge stack to determine the minimum level a rogue must be to flank the character.
Stand Ground (Ex): At 6th level a seneschal of silvera becomes very difficult to dislodge from her position or knock to the ground. Against bull rush attacks, she is treated as if she were one size category larger when making opposed Strength checks. A creature attempting an awesome blow against a seneschal of silvera must be at least two size categories larger in order to knock her flying 10 feet. She also gains a +4 bonus to her Strength or Dexterity check when defending against a trip attempt.
Mind Warding (Ex): Due to her fierce dedication to her mission, at 7th level a seneschal of silvera who is standing watch gains a +4 bonus on Will saves to resist mind-affecting magic. This bonus stacks with all other modifiers.
Active Defense (Ex): At 8th level a seneschal of silvera can still make attacks of opportunity while using total defense. These attacks of opportunity receive a -4 penalty on their attack rolls.
Seneschal of Silvera Prestige Class
Base
Class Attack Fort Ref Will
Level Level Save Save Save Special
1st +1 +2 +0 +2 Dodge threat, abjuration potency
2nd +2 +3 +0 +3 Uncanny dodge
3rd +3 +3 +1 +3 Group defense, delay advance
4th +4 +4 +1 +4 Guard's intuition
5th +5 +4 +1 +4 Improved uncanny dodge
6th +6 +5 +2 +5 Stand ground
7th +7 +5 +2 +5 Mind warding
8th +8 +6 +2 +6 Active defense
Seneschal of Silvera
The most dedicated followers of Silvera can choose to enter a sacred order that has long served as the guardians of holy places. These warders are highly trained in the arts of defense and observation, and learn the special skills needed to protect a fortress. They can be counted upon to defend their position to the death, if necessary, and inflict a great cost on any who would violate their ward.
A seneschal is often a leader among the guards, and in time will rise to the position of captain or commander of the entire company. She may be tasked by her temple with protecting a site that is more difficult to defend, or one that is more frequently subject to assault. If she has the necessary expertise, she may also be called upon to design improved defenses or construct a new fortification.
Most seneschal of silvera are fighters, rangers, clerics, or paladins, as other classes lack the requisite martial training and sophisticated skills needed to defend a fortification.
Hit Die: d10.
Requirements
To qualify to become a seneschal of silvera, a character must fulfill all the following criteria.
Alignment: Lawful Good or Lawful Neutral.
Base Attack Bonus: +5.
Skills: Search 2 ranks.
Feats: Alertness.
Spells: Ability to cast shield other as a divine spell.
Patron: Silvera.
Special: Must have spent at least a full season serving as a guard at an active fortification, such as a city wall or a castle.
Class Skills
The prestige class skills (and the key ability for each skill) are Climb (Str), Craft (Int), Diplomacy (Cha), Heal (Wis), Jump (Str), Knowledge (Engineering), Listen (Wis), Profession (Wis), Ride (Dex), Search (Int), Sense Motive (Wis), Spot (Wis), and Swim (Str).
Skill Points at Each Level: 4 + Int modifier.
Class Features
Weapon and Armor Proficiency: A seneschal of silvera is proficient with all simple and martial weapons, all types of armor, and shields.
Dodge Threat (Ex): A seneschal of silvera is expertly trained in techniques to avoid fatal blows by dodging aside at the last second. Whenever circumstances permit you to retain your Dexterity bonus to AC (if any), you can add your Wisdom modifier as a Dodge bonus to Armor Class when you are threatened by a critical hit. That is, whenever an opponent scores a threat against you, he must roll to hit your AC as adjusted by a positive Wisdom modifier in order to score a critical hit. This Wisdom modifier is cumulative with other Dodge bonuses to AC.
Abjuration Potency (Su): When casting a spell from the school of Abjuration, a seneschal of silvera's class levels are added to the levels of the class used to cast the spell for the purpose of determining the actual class level at which the spell is cast. Thus a character with 7 class levels of cleric and 4 class levels of seneschal of silvera would cast the abjuration spell spell immunity as an 11th-level cleric.
Uncanny Dodge (Ex): At 2nd level a seneschal of silvera retains his Dexterity bonus to AC (if any) even if he is caught flat-footed or struck by an invisible attacker. However, he still loses his Dexterity bonus to AC if immobilized. If a seneschal of silvera already has uncanny dodge from a different class, he automatically gains improved uncanny dodge (see below) instead.
Group Defense (Ex): A seneschal of silvera is highly trained in group defensive tactics. At 3rd level, any allies adjacent to the seneschal can not be flanked. In addition, whenever the seneschal of silvera is using total defense, any adjacent allies gain a +2 bonus to their AC against attacks of opportunity. This bonus stacks with any other AC modifiers.
Delay Advance (Ex): At 3rd level a seneschal is skilled at delaying the advance of an opponent around an exposed flank. The seneschal can attempt to block the movement from an adjacent square to another adjacent square, even if the advance is by means of a 5-ft.-step movement. For purposes of combat, this action is treated as an attack of opportunity, even though it is not triggered by the same conditions. Thus if a seneschal can only perform one attack of opportunity in a round, she can not perform an attack of opportunity in the same round as a delay advance.
The seneschal makes an unarmed melee touch attack against the advancing opponent, which does not trigger an attack of opportunity. If the attack succeeds, a Strength check is made which is opposed by the Defender's Strength or Dexterity check (whichever ability score has the higher modifier.) The bonuses and penalties to this check are identical to those of a Trip attack. If the attack is successful, the opponent is unable to advance and his move action ceases.
Guard's Intuition (Su): At 4th level, a seneschal of silvera developes an intuitive sense of danger while standing guard. When a seneschal of silvera remains awake within a 20-ft.-radius location for at least an hour, she receives a mental alarm each time a creature of Tiny or larger size enters the area or touches it. The alarm remains active until the seneschal departs the area. This is otherwise similar to the alarm spell (caster level equals Hit Dice.)
Improved Uncanny Dodge (Ex): At 5th level, a seneschal of silvera can no longer be flanked. This defense denies a rogue the ability to sneak attack the seneschal of silvera by flanking him, unless the attacker has at least four more rogue levels than the target has seneschal of silvera levels. If a character already has uncanny dodge (see above) from a second class, the character automatically gains improved uncanny dodge instead, and the levels from the classes that grant uncanny dodge stack to determine the minimum level a rogue must be to flank the character.
Stand Ground (Ex): At 6th level a seneschal of silvera becomes very difficult to dislodge from her position or knock to the ground. Against bull rush attacks, she is treated as if she were one size category larger when making opposed Strength checks. A creature attempting an awesome blow against a seneschal of silvera must be at least two size categories larger in order to knock her flying 10 feet. She also gains a +4 bonus to her Strength or Dexterity check when defending against a trip attempt.
Mind Warding (Ex): Due to her fierce dedication to her mission, at 7th level a seneschal of silvera who is standing watch gains a +4 bonus on Will saves to resist mind-affecting magic. This bonus stacks with all other modifiers.
Active Defense (Ex): At 8th level a seneschal of silvera can still make attacks of opportunity while using total defense. These attacks of opportunity receive a -4 penalty on their attack rolls.
Seneschal of Silvera Prestige Class
Base
Class Attack Fort Ref Will
Level Level Save Save Save Special
1st +1 +2 +0 +2 Dodge threat, abjuration potency
2nd +2 +3 +0 +3 Uncanny dodge
3rd +3 +3 +1 +3 Group defense, delay advance
4th +4 +4 +1 +4 Guard's intuition
5th +5 +4 +1 +4 Improved uncanny dodge
6th +6 +5 +2 +5 Stand ground
7th +7 +5 +2 +5 Mind warding
8th +8 +6 +2 +6 Active defense
