I mark on rare occasions when I tank. This is when the dps is just too plain awesome and I find my abilities to keep threat just not sufficient. I'm a terrible tank, but really... how hard is it to keep threat on a bunch of mobs?
Perhaps it should be amended in the OP's request: Tanks that can't hold threat should mark. :P Those tanks know who they are but don't want to admit it. They just spam "Rage of Hello" and do nothing else. If a mob peels off and goes after a healer, they just leave it. "Ain't nobody got time for dat!" Right? :p I see it all the time in daily roulette. When I was leveling my scholar, I marveled at Eos's ability to tank entire dungeons more effectively than the tanks I got. She could hold threat very well, and took less damage than these tanks (who often never bothered to update their gear or perhaps were missing entire pieces of gear entirely). I mean, I did Vale in duty finder and got a tank that had nothing on the right side...AT ALL! NO ACCESSORIES! :P
