Something to consider regarding healers being unnecessary is that we are approaching a new expansion where many people in this very thread and the rest of the game will encounter the time wasting tank effect at some point or another. The fact it's observable and the team has done nothing about this behavior is pretty incredible when you think about it.
With new content you're more likely to play with a broader range of players and experience more mistakes/wipes is what I mean. But it only takes a moderately aware unbalanced job to mitigate and sustain you to victory by themselves.
And the problem may get worse with time.