While tanking, especially on my guardian I hate ... yes my guardian hates ... every single player who thinks knockbacks are kewl to use while I try to keep the mobs on me ... nothing more amusing to me than seeing my main target get 'force pushed' away from me (while I try to keep the interrupts up on him) or sages(yes sages) running into melee range and scatter the whole pack of mobs all over the place, and lucky me: as guardian I have such wonderful (mid)ranged AoE abilities .... not.
These are days I am considering to just run as dps and go on /follow.
Seriously, this is so my pet peeve.
I go to the trouble of gathering people around me for the group to pick off/do aoe on, and some sorcs (imp obviously) thinks it's awesome to run in and blow everybody away.... multiple times. FYI people, that makes a tank's job harder.