Sad day for my zerker too because I picked Flexible Combat for him not knowing its also broken this build (and I can't use the mod to patch it on an active character ) So he's probably not going to be viable in the ID 
EDIT!: Realized today I didn't add enough possibly important details.. First, I'm pretty sure I didn't level Blood Frenzy up (in ID) until after my character was over level 50, so that could be part of the problem.. And I'm using two mods, Infinite 500 and Vulcus(??) something for ID that adds a new quest and shops to ID and a couple other things.. Okay, thats all!
(NON-BLOOD-FRENZY STUFF from here down, haha..)
Also, for ID, after a while the randomly generated equipment doesn't stand up to the two yellow items I've been using since floor 25-30 or so, which is Trident of the Tides and Khulmanar's Wrath.. Best tridents I've found barely get up to 100 damage the major majority of the time, and honestly, I think after floor/level 50 the equipment quits scaling up at all, making any honest run any farther than that a slowly losing battle
Doesn't look like the random-gen equipment will ever be better than those two weapons.. And the early-game boss enemies that appear in ID don't scale their defenses or attack power up very well either.. HP seems to be fine, but early bosses I find in the ID 20-35 levels higher than me are really easy (while some of the random-gen uber-enemies are absolute beasts, haha) I guess ID development isn't really a focus, but this game's Infinite Dungeon is a rarity among games, especially with these amazing classes and build combos to attempt deep diving with.. Just wish the scaling for weaponry got as epic as the enemies did Thanks!