In case nobody told you, you should probably use this (and screenshot the result in case it doesn't want to save for whatever reason).
To be fair... yeah, it kinda is. The whole gimmick of the Rogue class is being able to sit on enemies and deal massive damage thanks to the Cloak. There isn't really a good reason to put Berserk on top of Cloak when the Cloaking by itself already means you have more true DPS than most other classes (especially since it prevents them from teleporting to you).
Having a Cloak like this would just encourage Rogues to leech the whole dungeon, then teleport to the rusher, cloak in on the boss and deal huge damage with Berserk.
There's nothing wrong with giving Red Demons their own UT drop per se, but when it's pretty much a straight upgrade from the t6 ability it becomes a balancing issue.
Then go for it.
Everyone has emotions, but some are more mature in their way of handling them than others.