It's lots of fun to get 5x rip/rake up on someone tanking Garrosh, which is undispellable (except for dwarf racial) and almost unhealable due to the lag their own raid created, then watch the tank die and Garrosh pick off each player one by one.

On the other hand, ruinous can be downright annoying if you are just trying to get dailies done or relax. You almost have to have a stealth class to be able to get around them and get something done.

It is too bad BCJ is gone now on kil'jaeden. I remember them spamming "Need more stormwind mage tower will summon" for hours in /2. Fun times.