Couple years ago I went crazy with Weakauras, making and collecting ~3000 of them. Learned a lot about lua and the Wow API in the process. I went a little overboard with audio etc. (If you wanna see the craziness google machinelf wow youtube) It was probably the single biggest project of my life, easily dwarfing anything I had done professionally. Somewhere a while back I went through and took out all CPU intensive auras, constantly testing FPS.
I assembled complete suites of auras for all 34 class/specs. I learned a lot about priorities and rotations in the process. But as a player I was mediocre at best. I learned an insane amount of knowledge about my class and the game but my dps was sunstandard. Everything seemed to be slo mo and sloshy during heavy combat phases. I made sure to select load options very carefully. But when my guild started running 25 mans my performance was so bad I knew my days were numbered and had to make drastic changes.
So in desperation I tried everything I could to reduce lag. Put all graphics to minimum. Disabled almost all addons, switched from Recount to Skada then finally Tiny DPS. Still laggy.
Disabled most auras for Raid 25. Better. On a lark I disabled weakauras and re-enabled a couple slim addons that WA had replaced.
My dps went up ~40%.
The game felt amazing and fast again. I was able to do things I hadn't been able to before. I was forced to be in the moment and pay more attention to raid awareness and visually eyeballing things.
Somehow in my rush for UI tweaking and addons I forgot what the game was like when it runs smoothly. I've decided to keep Weakauras disabled until I have a computer so fast I can't tell any lag.
Let this be a cautionary tale for anyone who has gone weakauras crazy. The addon is freaking amazing, but you are slowly piling on more and more load on your processor the more you get addicted. Every once in a while disable weakauras and get into some heavy shit (25 man, AV, etc) and see if there's a huge difference in FPS/lag.
In case anyone is curious, I have a 6 core 2.8GHz processor and 8 gigs of RAM and an AMD Radeon 6570. I bought it in 2011.
It can happen to anyone! Don't do what I did and get tunnel vision!