Dear ClassLoot Dev.
First of all i'd like to thank you for this wonderful addition to the community.
Excuse me for not using the regular form but i think ill be more descriptive in my way.
On with the problem then.

After getting my first piece of gear on my alt and checking the tooltip i noticed a massive drop in my framerate.
After some testing at orgrimmar and by using the addon : Addon Profiler i noticed that one of the most CPU hogging addons where : Tip Tac, Gearscore Lite and Classloot. Although after checking other parts of my gear that weren't part of raiding so classloot wasn't active i noticed that tiptac and gearscore lite had a reduced ammount of cpu usage my frame rate was normal, leading me to think that ClassLoot was forcing a really quick refresh of the tooltip.
I also confirmed this with my main having the same results.
Tried this on Versions : V1.7.2 and r126 (Installed through Curse Client).
original item was "bracers of dark mending".
Possible other addons being problematic with classloot : TipTac, GearScore Lite, RatingBuster, Bagnon Forever.