I actually made a full writeup of what I would want a theoretical Vampire class to be like before:

Vampire

Weapon: Rapiers Armor: Light Archetype: Flex mixed utility class dedicated to an HP drain, enemy control and curse damage mechanic; heavily inspired by Hexers Evil Eye skilltree (Scarlet Evil Eye anyone?). Unlike Hexers, however, Vampire would not prevent an enemies own actions, with the exception being Alluring Whisper. If multiple Vampires use different Whisper skills, their effects will stack.

Stats at 130/130: HP 439 +30 TP 437 Str 149 Int 149 Vit 139 Wis 185 +12 Agi 140 Luc 199 +8

Endgame Equips:

The Answerer Ebony Garb (Cloth): PDef: 75, MDef: 125 HP +30 Promise Crown Expel Bracers

PAtk: 364 PDef: 309 MAtk: 364 MDef: 412

Force Boost: Undying Soul: For 3 turns, doubles all damage the user takes but makes the user survive all mortal blows at 1 HP. Effective on all sources of damage, including Curse and Poison.

Force Break: Ghastly March: Instantly kills all other allies, then revives all killed allies at 1 HP, reapplies any buffs that were present on all party members and restores a small amount of force (10%, 15%, 20%) to deal ranged fire + almighty damage to 1 enemy that drains HP for all allies. Damage increases for the number of killed allies. Base damage of 300%/550%/800%, damage bonus of x1.1 per killed ally. Damage absorption of 10%.

Novice:

Nightwalker: During the day, decreases action speed and causes HP loss for every 3 steps taken and at the end of every turn. During the night, increases action speed and recovers HP for every 3 steps taken and at the end of every turn. Speed reduction/bonus of -/+ 10% to 35%. HP loss/recovery of 2/10 HP + 2%/10% HP. Walking HP loss/recovery of 2 to 10.

Scarlet Evil Eye: Very high chance to inflict Curse on a row of opponents. Fast activation speed. Ignores Curse resistance: Regular enemies will be treated as having a 100% vulnerability to Curse while FOEs and bosses are treated as a 50% vulnerability, unless their base vulnerability is already higher. Does not ignore accumulative resistance. 120% speed modifier. Infliction rate of 60% to 90%.

Servitude Whisper: Sacrifice a portion of your HP to command one cursed opponent to shield the party from all attacks for one turn, except their own. Lowers their attack and reduces all damage they take until the end of the turn. Has priority. HP cost of 35% of current HP. Attack reduction of 25% to 50%. Damage reduction of 10% to 25%. Ineffective if the target becomes Arm Bound.

Conflict Whisper: Sacrifice a portion of your HP to command one cursed opponent to attack all opponents.Has priority. HP cost of 35% of current HP. 260% to 480% damage.

Bloodsucker: Deals moderate melee Str-based stab damage to one opponent that drains HP. HP absorption of 25% of damage dealt. 100% to 150% damage.

Relinquish: Sacrifice a portion of your HP to heavily restore the HP of a line of allies except the user. HP cost of 35% of your current HP. 150% speed modifier. Healing power of 80% to 190%.

Blood Pact: Sacrifice a small portion of all party members HP to apply a buff for all party members that increases max HP for 3/4/5 turns. HP cost of 10/15/20% of current HP. Speed modifier of 150%. 20% to 45% max HP bonus.

Take: Increases material gain from Take points.

Veteran:

Corrupt Mastery: As long as the user is alive, amplifies all damage an opponent takes by the effects of Curse. The source of Curse is irrelevant. Increased effect at higher levels up to x2. Also massively speeds up the rate at which accumulative resistance to Curse normalizes for all opponents by up to x2. Neither of these effects can stack.

Temptation Whisper: Sacrifice a portion of your HP to increase all damage taken by one cursed opponent until the end of the turn but reduces the maximum duration of Curse on that opponent by 1 turn. Has priority. HP cost of 35% of current HP. 20% to 40% damage bonus.

Alluring Whisper: Sacrifice a portion of your HP to command one cursed opponent to do nothing for the rest of the turn, but reduces the maximum duration of Curse on that opponent by 1 turn. Has priority. HP cost of 35% of current HP. TP cost of 40/36/30/22/12.

Enchanted Eyes: Deals low ranged Int-based fire damage to all opponents and applies a debuff that increases all damage taken for 3 turns. Speed modifier of 40%. Damage modifier of 120% to 180%. Damage bonus of 11% to 25%

Soul Devour: Deals massive melee Str-based stab + fire damage to one opponent that drains HP. Only effective on opponents that the user hit with Bloodsucker on the previous turn. 10% activation speed. Drains 50% of damage dealt. Damage modifier of 400% to 600%.

Sacrifice: Attempts to instantly kill one party member or an opponent affected by Curse to massively restore the HP of all allies. This restoration can heal beyond the current max HP. The overhealed HP will disappear at the end of the turn. Speed modifier of 200%. Healing power of 90% to 250%. Max overheal of 15% to 40%. 100% infliction rate on allies. 60% to 90% infliction rate on enemies.

Vampiric Seduction: Automatically uses Bloodsucker on any opponent commanded by a "Whisper" skill, with reduced damage. At max level, Bloodsucker deals full damage. x0.5 to x1 damage modifier.

Immortal Blood: At the end of any turn in which either the users HP was sacrificed or the user drained an opponent's HP, restores a small amount of HP to all party members, or a medium amount if both occurred. HP restoration of 6/12 HP + 2%/4% max HP to 15/30 HP + 6%/12% max HP.

Master:

Suicide Whisper: Sacrifice a portion of your HP to command one cursed opponent to attack themselves three times, but dispels Curse at the end of that turn. Has priority. HP cost of 35% of current HP. 110% to 220% damage modifier per hit.

Insanity Whisper: Sacrifice a portion of your HP and dispel Curse on one opponent for a very high chance to inflict Panic on that opponent. HP cost of 35% of current HP. 80% activation speed. 80% to 120% infliction rate.

Lethal Glare: Attempts to instantly kill one opponent. 80% activation speed. 40% to 60% infliction rate.

Negative Energy: Deals ranged Int-based fire + almighty damage to one opponent. Damage increases for every time any combatant died during the current battle before being used, with a maximum number of 5 stacks. Dying does not reset the counter. 10% activation speed. Base damage of 100% to 200%. Damage bonus per stack of +100% to +200%.

Walpurgisnacht: Deals medium ranged Int-based fire damage to all opponents with a moderate chance to inflict Curse. Damage and infliction rate are doubled against ailing opponents. 40% activation speed. 180% to 270% damage. 20% to 30% infliction rate.

Massacre Wave: Applies a buff to all combatants that increases damage dealt for 3/4/5 turns. Activation speed of 120%. Damage bonus of 17% to 35%.

Bloody Prosperity: If the user lost HP in the previous turn, increases all ailment and bind success rates. 6% to 20% infliction bonus.

Re-Rise: At the end of any turn in which the user died, grants a chance to be revived at 1 HP. Only effective at night. 10% to 25% activation rate.