Alternative suggestion: Bleed becomes a conditional debuff rather than stacked on the DOTs. My take would be
Womp! :
Deal Physical damage to target enemy and inflict Damage Over Time for 2 turns. If the target was debuffed, gain 20% turn meter. If Wampa isn't debuffed, gain 20% turn meter. If the target already has Damage Over Time, instead inflict 1 stack of Bleed (max 6) until the end of the encounter, which can't be dispelled. If the target has Damage Over Time or Bleed, there is a 10% chance to Stun them for 1 turn.
Bleed: -5% Speed and Tenacity, and lose 5% Health each turn; remove 1 stack when any Health is recovered
Icebreaker :
Dispel all debuffs on Wampa. Deal Physical damage to all enemies and Daze them for 2 turns. Wampa gains Protection Up (150%) until the next time this ability is used, which can't be Dispelled or prevented.
Furious Foe :
Inflict Healing Immunity on all enemies for 2 turns, which can't be Evaded. Wampa gains 40% Accuracy, 40% Critical Chance, and 40% Offense (stacking) until the end of the encounter. Wampa gains 10% Turn Meter for each empty ally slot and each active enemy. This ability starts on cooldown.
Howling Rage :
While Wampa has Protection Up, it has +20% Counter Chance, +50% Defense, +50% Offense, and +50% Tenacity.
Cornered Beast :
Wampa has +50% Counter Chance. Wampa has +10% Counter Chance, +5% Health Steal, and +5% Offense for each Damage Over Time on each enemy.
While in Grand Arenas: Wampa gains +100% Tenacity and is immune to Stun. If there are no other active allies at the start of battle, Wampa gains +100% Defense, Max Health, Max Protection, and Offense, doubled if there is only 1 active enemy at the start of battle. Whenever Wampa is damaged by an attack, inflict 2 stacks of Damage Over Time for 3 turns on the attacking enemy, which can't be evaded or resisted, the cooldown of Furious Foe is reduced by 1, and gain +30% Tenacity (stacking) until the end of the encounter.
A tamer touch up, with added Defense on its first unique and exactly your suggestion for the Omi. Since Wampa goes solo, it doesn't gain TM for its defeated allies because there are none, so it instead gains bonuses when it has no allies, similar to Fennec's lead being better when she is solo (though no one ever uses her that way. Ever), toning the TM down from 15% to 10%. The Stun mechanic is reintroduced but at a much less likely chance, because Wampa will almost always be hitting enemies and there still needs to be some balance. Bleed replaces DOTs if the target already has DOTs.