So SEA is using more than 3 times as much CPU as Threat. Of course UNIT_AURA is fired an awful lot in this particular fight, but it just exemplifies how horrible SEA really is. It's very bad especially as the tank. On phase transitions, the entire raids gets a different debuff, that's probably 2 UNIT_AURA events for every raid member. I have to time my shield slam, but in the exact frame where I have to be as quick as possible, SEA causes frame lag. Not funny.
Here's a little quote from the interview at curse.
Antiarc: Well, Omen is obviously inspired by KTM, but I've attempted to improve on the design. The primary reason that Omen (well, its backing library, Threat-1.0) was written is because KTM brute-forces its threat estimates by polling a large number of values every so often. When we gained CPU profiling in WoW, I noticed that KTM was eating significantly more amounts of CPU time than any other of my mods, even while idle. There was a bit of a flamewar going on over this issue already, but what it basically came down to is that Kenco (KTM's author) didn't have any intent to change KTM's design to be more efficient, so I decided that I could do it better. Omen is empirically, by design, more CPU-friendly, which should improve the user's framerates, though that point is contested by Kenco. :)