Eh true. Would probably be better balanced with +1 caster level every even dragon disciple level. And drop the BAB req.
But now the class has a weird thing as a transition phase going from spellcaster to warrior. It should probably be the opposite to make sense. Maybe require +7 BAB and spontaneous spells of any level but grant full spellcasting and half BAB. Because spellcasters are weak at low levels and warriors weak at high levels so making a prestige class that goes from weakest to weakest makes no sense.
With this a Bard 10 can qualify with full bardic spellcasting. 
A sorcerer 6 full BAB class 4 qualifies for 16th level spellcasting.
A sorcerer 2 full BAB class 6 qualifies for 14th level spellcasting.
Kind of counter-intuitive. I think I'll just stick with half spellcasting. Makes more sense as a fighter/barbarian-oriented class.
DRAGON DISCIPLE
Hit Die: d12.
Requirements
To qualify to become a dragon disciple, a character must fulfill all the following criteria.
Race: Any nondragon (cannot already be a half-dragon).
Skills: Knowledge (arcana) 8 ranks.
Languages: Draconic.
Spellcasting: Ability to cast arcane spells without preparation.
Class Skills
The dragon disciple’s class skills (and the key ability for each skill) are Concentration (Con), Craft (Int), Diplomacy (Cha), Escape Artist (Dex), Gather Information (Cha), Knowledge (all skills, taken individually) (Int), Listen (Wis), Profession (Wis), Search (Int), Speak Language (Int), Spellcraft (Int), and Spot (Wis).
Skill Points at Each Level: 2 + Int modifier.
Table: The Dragon Disciple
	
	
	
		Code:
	
	
		Level     BAB      Fort     Ref      Will     Spellcaster Level
1st       +1       +2       +0       +2       -
2nd       +2       +3       +0       +3       +1
3rd       +3       +3       +1       +3       -
4th       +4       +4       +1       +4       +1
5th       +5       +4       +1       +4       -
6th       +6       +5       +2       +5       +1
7th       +7       +5       +2       +5       -
8th       +8       +6       +2       +6       +1
9th       +9       +6       +3       +6       -
10th      +10      +7       +3       +7       +1
Level     Breath Weapon     Ability boost     Special
1st       1d6               +2 str            Low-light vision
2nd       2d6                     
3rd       3d6               +2 con            Darkvision 60'
4th       4d6                     
5th       5d6               +2 int            Blindsense 30'
6th       6d6                      
7th       7d6               +2 cha            Immunity to sleep
8th       8d6                                 Immunity to paralysis effects
9th       9d6               +2 str            Blindsense 60'
10th      10d6                                Immunity to breath energy type
	 
 Class Features
All of the following are Class Features of the dragon disciple prestige class.
Weapon and Armor Proficiency: Dragon disciples gain no proficiency with any weapon or armor.
Ability Boost (Ex): As a dragon disciple gains levels in this prestige class, his ability scores increase and stack as if through level advancement
Breath Weapon (Su): At 2nd level, a dragon disciple gains a minor breath weapon. The type (acid, cold, fire, lightning) and shape (line or cone) are determined by the dragon disciple. 
The breath weapon can be used once every 5 rounds. The DC of the breath weapon is 10 + class level + Con modifier. 
Use all the rules for dragon breath weapons except as specified here.
A line-shaped breath weapon is 5 feet high, 5 feet wide, and 60 feet long. A cone-shaped breath weapon is 30 feet long.
Blindsense (Ex): At 5th level, the dragon disciple gains blindsense with a range of 30 feet. Using nonvisual senses the dragon disciple notices things it cannot see. He usually does not need to make Spot or Listen checks to notice and pinpoint the location of creatures within range of his blindsense ability, provided that he has line of effect to that creature.
Any opponent the dragon disciple cannot see still has total concealment against him, and the dragon disciple still has the normal miss chance when attacking foes that have concealment. Visibility still affects the movement of a creature with blindsense. A creature with blindsense is still denied its Dexterity bonus to Armor Class against attacks from creatures it cannot see. At 9th level, the range of this ability increases to 60 feet.