Go with the Bard.
Play as a support unit/backup healer.
Use Dispel Magic to counter the Lich's spellcasting. Spring attack around the battlefield setting up flanking and fighting with your keen rapier.
Buff the party with Bardic performances, and judicious use of Moment of Greatness.
After you kill the lich, be sure to use Treasure Map to find out where all his best loot is stashed.
Here's the build I would go with ...
OGREHATESCOMPUTERS'S ELF BARD CR 6
Male Elf Bard 7
CG Medium Humanoid (Elf)
Init +5; Senses Low-Light Vision; Perception +12
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DEFENSE
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AC 21, touch 14, flat-footed 17. . (+7 armor, +3 Dex, +1 dodge)
hp 35 (7d8)
Fort +2, Ref +8, Will +5
Immune sleep; Resist Elven Immunities
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OFFENSE
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Spd 20 ft.
Melee +1 Keen Rapier +8 (1d6+1/15-20/x2)
Special Attacks Bardic Performance (move action) (20 rounds/day), Bardic Performance: Countersong, Bardic Performance: Distraction, Bardic Performance: Fascinate (DC 17), Bardic Performance: Inspire Competence +3, Bardic Performance: Inspire Courage +2, Bardic Performance: Suggestion (DC 17)
Bard Spells Known (CL 7, +7 melee touch, +7 ranged touch):
3 (2/day) Cure Serious Wounds (DC 17), Dispel Magic
2 (4/day) Sound Burst (DC 16), Cure Moderate Wounds (DC 16), Create Treasure Map, Ghostbane Dirge (DC 16)
1 (5/day) Comprehend Languages (DC 15), Hideous Laughter (DC 15), Cure Light Wounds (DC 15), Chord of Shards (DC 15), Moment of Greatness
0 (at will) Know Direction (DC 14), Read Magic (DC 14), Detect Magic, Mending, Prestidigitation (DC 14), Message
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STATISTICS
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Str 10, Dex 16, Con 10, Int 13, Wis 10, Cha 19
Base Atk +5; CMB +5; CMD 19
Feats Bard Weapon Proficiencies, Dodge, Elven Weapon Proficiencies, Mobility, Spring Attack, Weapon Finesse
Traits Dilettante Artist: Perform (Sing), Perform (Dance), Warrior of Old
Skills Acrobatics +14, Bluff +15, Climb +7, Diplomacy +5, Escape Artist +0, Fly +14, Heal +7, Perception +12, Perform (Dance) +14, Perform (Sing) +15, Ride +0, Sense Motive +15, Spellcraft +11, Stealth +10, Swim -3, Use Magic Device +14
Languages Common, Draconic, Elven
SQ Bardic Knowledge +3 (Ex), Elven Magic, Lore Master (1/day) (Ex), Versatile Dance +14 (Ex), Versatile Singing +15 (Ex), Well Versed (Ex)
Combat Gear +1 Keen Rapier, +1 Mithral Breastplate; Other Gear Wand of Dispel Magic
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SPECIAL ABILITIES
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Bardic Knowledge +3 (Ex) Add + 3 to all knowledge skill checks.
Bardic Performance (move action) (20 rounds/day) Your performances can create magical effects.
Bardic Performance: Countersong (Su) Counter magical effects that depend on sound.
Bardic Performance: Distraction (Su) Counter magical effects that depend on sight.
Bardic Performance: Fascinate (DC 17) (Su) One or more creatures becomes fascinated with you.
Bardic Performance: Inspire Competence +3 (Su) +2 competence bonus for one ally on a skill check.
Bardic Performance: Inspire Courage +2 (Su) Morale bonus on some saving throws, attack and damage rolls.
Bardic Performance: Suggestion (DC 17) (Sp) Make a Suggestion to one Fascinated creature.
Dilettante Artist: Perform (Sing), Perform (Dance) You gain a +1 trait bonus to one category of Perform checks and a +1 trait bonus to Diplomacy checks. One of these skills (your choice) is always a class skill for you.
Elven Immunities +2 save bonus vs Enchantments.
Elven Immunities - Sleep You are immune to Sleep effects.
Elven Magic +2 racial bonus on caster checks to overcome spell resistance. +2 to spellcraft checks to determine the properties of a magic item.
Lore Master (1/day) (Ex) Take 10 on knowledge checks, and 1/day take 20 as a standard action.
Low-Light Vision See twice as far as a human in low light, distinguishing color and detail.
Mobility +4 to AC against some attacks of opportunity.
Spring Attack You can move - attack - move when attacking with a melee weapon.
Versatile Dance +14 (Ex) You may substitute the final value of your Perform: Dance skill for Acrobatics or Fly checks
Versatile Singing +15 (Ex) You may substitute the final value of your Perform: Sing skill for Bluff or Sense Motive checks
Well Versed (Ex) +4 save vs. bardic performance, sonic, and language-dependent effects.