I welcome the prospect of rare/champion packs being Diablo III's greatest challenge. They offer more diversity than bosses can. I like how each pack will offer a different kind of battle. I find even just having two traits in Nightmare mode can be quite the fight- can only imagine what four is like in Inferno mode. I'm picturing myself chasing a treasure goblin leading me into two inferno champion packs which can mean eight different traits. I've already ran into two packs in Nightmare a few times, so it can certainly happen (thanks to traits like Nightmare).
As a Barbarian, I find Jailer to be the most difficult ability. If it's on a heavy hitting mob and you're already low on life it can mean certain death. If you combine that with other traits like Molten, by the gods I wish you Hardcore players luck.
I believe this is a full list of possible monster traits: Arcane Enchanted, Avenger, Desecrator, Electrified, Extra Health, Fast, Fire Chains, Frozen, Health Link, Horde, Illusionist, Invulnerable MInions, Jailer, Knockback, Missle Dampening, Molten, Mortar, Nightmarish, Plagued, Shielding, Teleporter, Thorns, Vamperic, Vortex, and Waller.
As a Barbarian, I find Jailer to be the most difficult ability. If it's on a heavy hitting mob and you're already low on life it can mean certain death. If you combine that with other traits like Molten, by the gods I wish you Hardcore players luck.
I believe this is a full list of possible monster traits: Arcane Enchanted, Avenger, Desecrator, Electrified, Extra Health, Fast, Fire Chains, Frozen, Health Link, Horde, Illusionist, Invulnerable MInions, Jailer, Knockback, Missle Dampening, Molten, Mortar, Nightmarish, Plagued, Shielding, Teleporter, Thorns, Vamperic, Vortex, and Waller.