ES warlock destroys T5 heralds fastest of pretty much any build in the game, nearly instantly
blood boil warlock isn't nearly as fast, but does it very safely and reasonably fast
abyss warlock can't even scratch them
nova sorcs and javazons can't tank heralds or keep their merc alive against them. All warlock has to do is deathmark his demon in front of the heralds and they'll attack it instead of his merc
Heralds have the problem of being astronomical amounts of HP and huge damage output, because they're getting +3000% base life / +250% damage (14x minions with +750% / +50%).
They can easily hit 2 million HP like p8 baal, but because of that massive base damage multiplier and stacking auras they can hit for 1000+
But they're still generally the same easily kited easily tanked crap pvm mobs, if you are facing a bunch of zombies with 2 million hp 1000 damage okay, you just don't get in melee range of them. Your merc will die instantly if he takes aggro, but your demon can tank them pretty near infinitely especially if you use engorge to full juv him. A nova sorc has to get in range to cast it, without getting hit. A javazon uses a lot of mana without any MAEK to throw furies at them, but will lose conviction aura as her merc dies and getting in range to poke is suicide until its just one herald left and even then she can get bodied.
Strange you mentioned blood boil and abyss but not fire