The thing is, I say you need full DL for DFs because you're trying to get every advantage.
For example, you say a healer died during weight of the lands. No one should be dying from that, but maybe he was trying to land a heal that would save your (the tank's) life. Maybe if you had 1k more health, he wouldn't have had to risk getting hit with weight. Very little is black or white, right or wrong. If people have full DFs, less risks need to be taken by healers trying to keep everyone alive etc. You can't just say a healer died because he's a noob unless you know the whole story.
If you're going in with less than full DF then other members in the group might have to take risks which might lead to a wipe, to keep you alive. It might seem it was their fault and it's easy to throw blame on people dying to aoes and stuff, but unless you're in full DF you're not doing your part.
