if the tank got hit for more damage than you can heal then the tank was either pulling more than one group or you were in savage content. i guess it's the first case.
SE can not do much about it. it's a problem caused by the community. when a tank thinks "i am not good enough, i should pull small", then the next DD or healer will run ahead and pull the next group of enemys. a tank don't really have a choice. either he pulls big or the party pulls big for him. but if he can't handle big pulls yet, it will probably lead to a wipe.
i remember when i was new at tanking and the healer and both DDs were running ahead, pulling the next group and let me die. if you pull small as a tank you do it wrong. and if you start pulling big because your teammates force you, you are wrong too, because you are not ready for these pulls.
SE can not do much about it, maybe put even more walls into the dungeons? but i don't think that is what we want...
