Some people may not agree with me, but I personally think it is against the spirit of the game for % damage to be the only viable way to play at a higher level, especially with ideas like daily duels being implemented. Zack as stated before he wants all creatures to be viable - this is unfortunately not the case. Alternatively, you could consider them viable, and percentage builds abusive due to reaching an essentially infinite ability to ignore enemy level. For one thing, this almost completely invalidates the point of nether creatures (and with certain enemy abilities, they’re arguably worse). It also makes the feeling of advancement pointless - you know you’re set for anything barring bad RNG, so your own level has no meaning and neither does the level of your creatures.
I think there should be some kind of hoser that makes it if your creatures are vastly outleveled, something goes in that weakens % abilities; like a troll arsonist doing 35% damage to a random enemy (up to 250% of own maximum health (as a random number, not balanced). Essentially, still forcing you to change/upgrade/level your team rather than a setup raising your maximum realm level feasible from 30 to 2.1 billion. I think the stat-ignoring setups are against the spirit of the game, honestly, and restrict build variety and leaves dozens (and probably well over a hundred) of creatures useless.
I know this may be a controversial idea, but it just doesn’t seem balanced or feel good progression-wise. If your party can beat 99% (barring awful RNG teams) of level 200 teams and 99% of level 2 billon teams, why continue to play? You’ve essentially reached infinite power.