Actually Levi doesn't penalize casters at all because NO ONE can hit Levi during the dodging phases. Tail and head each can only take one form of damage. Tanks don't have to swap like many of the other endgame Trials but they do have add management and a stun component. The healers get a debuff they need to work together to overcome. YOu have to hit a switch twice. It's not nearly as punishing on higher latency players as Titan. Based on what you're saying Levi is the perfect Primal. Also...Moggle Mog EX. Has tank swaps. DPS need to be sure to manage damage so as to maximize the damage to Moggle when he heals the minions. Healers need to be mindful to remove debuffs. All the AoEs are forgiving so the dodging mechanics are actually quite minimal and not at all detrimental to the casters. Especially if your DPS are interrupting the bigger booms like Holy and Flare.