I wouldn't necessarily say using hate/resolve points makes adversaries too tough, or at least not just that.
There are interesting effects to running out of hate for mobs, from specific fell abilities/effects to the generic weary condition.
♦ The Lore master can reduce an adversary’s Hate or
Resolve score to make them gain (1d) on a die roll
during combat (generally, attack or Protection rolls).
♦ Often, an expenditure of Hate or Resolve is required
by several Fell Abilities (see next page).
♦ Finally, if a creature begins a round without Hate or
Resolve points, it is considered Weary.
personally I probably would use the points more for the specific abilities, as they might have more variation than just adding a dice and for some of the mobs it's probably required to get their specific flair mechanically across.
Before I would stop using them because they make single mobs too strong, I probably would reduce the amount of mobs.