Its not that insanely fast ticking arcane sentry, its not gouts of lava under your feet, its not knockback or illusionist. Its not molten or nightmarish either. Its not even battle.net lag or rubberbanding.
The true bane of hardcore characters in D3 is waller. Especially in tight spaces. Thank god I havent met any waller/horde packs in inferno yet.
Waller is a murder in inferno unless you have a leap-like skill (I don't, because leap sucks for farming).
My last 60 death was to being chain frozen + desec-ed. My fault though, charged with WOTB on CD. Entirely avoidable. I don't ever fight wallers without both big cooldowns... unless they are completely harmless (e.g. no offensive affixes). If all my cooldowns are up, I don't really care what the boss does. Waller/Arcane/Frozen/Desec? No problem. Charge, Wotb, Quake, IP, collect loot.
Waller + Desecrator in a tight place is a tough fight, but it's usually pretty easy as waller typically helps me kite while Locusts do damage. The thing that makes the combination potentially lethal isn't the fact that there's a possibility of getting stuck on desecrated ground with no way out several times in a row. It's the fact that the fight usually has a favourable outcome combined with the fact I don't want to lose my NV stacks. Get rid of the NV stacks and I'll run every time as I've got nothing to lose. Get rid of the typically favourable outcome and I'll run every time as I've got nothing to gain.
Naturally fast monsters with the fast modifier would kill me if I ever gave them the opportunity, but I don't, so they won't. It's something like waller/desecrator in a hallway that's going to get my ear. If a crash doesn't get it first.
With perfect timing you can leap out of freeze too.
Unless I'm missing something, you can leap to avoid getting frozen if you're in the air when they pop, but once you're frozen, if WoTB is on cooldown, you're pretty helpless to break out of it if they keep the freeze coming when you're already frozen.
Chain freeze is way more dangerous than waller IMO - but then again, I'm playing a barbarian who can leap out of waller packs...
I don't know why this has never occured to me to do this! Coming from a DH where waller means stay calm and pop SS I don't know why my first instinct with the barb is when the red mist descends, is to kill them before they kill me in the little walled arena its created!
Edit: for me its +fast, on normal fast means they get to you and die quicker but its on NM onwards where they can bring what other nasty modifier to you quicker..