Hmm. I think that's about the worst for me, too. Invulnerable Minions, Horde, Reflect Damage, and either Fast or Teleport might tie or come in at a close second.
I did run into, of all things, a Fallen Shaman + Fallen pack with Invulnerable Minions and Fast; it was pretty nasty. I couldn't keep the fallen off of me very long and any time I damaged the Shaman he would run away (quickly, being Fast). Died too often to put them down; I eventually parked that pack out of the way.
Its frustrating with those affixes! How is one suppose to get past them?
I dont know about worst, but the funniest I've seen is those charging 'buffalo' type critters (cant remember their proper name) in act 1 with Waller. They form the walls and pen themselves in from charge attack for an easy kill.
i was fighting a champ pack of the guys in act 1 that do the big slam attack... vortex, jailor, frozen, defiler. i'd try to run away from the ice balls to get vortexed in, frozen then slammed by all 4 of them. tried 5 lives on them. most of my lives lasted under 15 seconds.
Another goodie is teleport + firechains. They appear on top of you, the firechains touch you, melted.
For ranged, fast base creatures like leapers, spiderlings, or the fast mummies are terrifying. Add fast and it's impossible. Ever have a champ pack of fallen grunts get raged from a nearby overlord? Oh god.
Hmm. Well, my DH has some okay defensive gear so I don't get killed instantly by fire chains, but a really fast base type + teleport + firechains, or anything with fast + teleport + fire chains is pretty nasty.
I'm having a hard time with Reflect Damage monsters.
When I see a rare/champion pack I start spamming lightning balls and arrows and when I see I'm dead. Even when I'm smart enough to actually look for the type of monsters and start the fire-kite-fire dance, my life goes down really fast, I usually die 2-3 times before kill them.
Is there an easy-ier way to deal with them?
I'm actually at Hell Act 2, level 56, 20k life and 12k DPS.