It's not gamebreaking, just as ~95% of the others bugs mentioned here. I'm playing a Cipher on hard difficulty and had this bug since I equipped that amulet as well. It's annoying and kinda spoils the fun of playing a Cipher but it's by no means at all gamebreaking...
You guys should think a bit more before you call a bug gambreaking. A bug might make the game less fun or even frustrating to play but gamebreaking means you literaly can't play the game anymore, even if you could get over being annoyed or frustrated about a bug. I have bugs too, I'm annoyed and sometimes frustrated too that the game got through QA in this state but this overdramatizing that is going on here, calling every little bug gamebreaking is ridiculous...
Also, some of you who cry for patches and demand to get the patch yesterday should maybe give this http://mrlizard.com/rants/why-havent-they-fixed-this-bug/ a read, even though it's mainly about MMOs it also applies to other games.
just my 2 cents
Yea the CIpher thing is just mildly annoying.
The Stats becoming Insane ruins the fun of the challenge. (Unkillable Tanks = boring)
The Ranger pet disappearing though, that's potentially gamebreaking, it'll corrupt your save and prevent you from being able to zone. So I suggest do not play or use a Ranger, unless you don't mind losing progress and save a lot. (Not just Quicksave and Auto-save)