I feel this is where desire for game design meets the harsh reality of MMO needs. The reality is that what you want can probably easily be designed by the team, but it would result in dungeons which most people won't want to run multiple times. This will mean that for new players as time goes by, it gets increasingly harder to queue for dungeons at all. Since they are basically going to be -done- after each player 100% clears it. MMO players who form the bread and butter of queues want straightforward stuff they can quickly power through daily to grind materials. That's just how it is.
Yeah I understand. Most MMO players aren't very open to changing that frame of mind either, so attempts to focus more on actual fun content vs. carrot-on-a-stick grinds will be met with fierce resistance. I can dream though.