So yesterday I decided to try DSA with a few people with all of our champion points for a laugh, and to try out destro staves, which I've never used. I was using a sharpened master fire staff. After a while in the dungeon using crushing shock, destructive reach and heavy attacks, I noticed my magicka was incredibly high, at 60k. Once I noticed this, I kept an eye on it and it just kept going up until it eventually hit 100k. I looked at my passives and noticed that the I had dozens of the same passive enabled from the master destro staff and each one was increasing my magicka and destructive reach damage. By the end, swallow soul was healing for 20k a tick and I was able to kill the last boss in about 5 heavy attacks.

The reason I'm posting this is that I have not been able to recreate the bug. I haven't tried going into DSA again, but I wasn't able to get this to happen again outside. Once I left DSA, the stacking passives vanished. If anyone can figure out the bug and report it, that'd probably be good. As fun as it was, this sort of thing completely breaks the game.

I should also note that during almost my entire playthrough of DSA and most of the rest of the session, ultimate regen was completely not working at all. I'm not sure if that has anything to do with this bug.