This needs to be stopped, and immediately.

[Lucke]

First I guess it's a good thing both story dungeons can be solo healed, you leaving just opens the door for someone else that is there to actually get something done.
Second if the reward was too low, you are right, people would stop running it and new people would once again be on the forums complaining that it takes them over four hours for a party to form. This was already an issue and the reason that the main scenario roulette with it's current rewards was added.

I can pretty much guaran-godsdamn-tee if the healer(s) or tank(s) left, you'll be sitting on your ass for awhile. If they leave, you're best bet to to leave and requeue because you'll be waiting for a rep of those 2 jobs for awhile. And the point of SRs is to "GOTTA GO FAST". Sitting on your butts waiting for the rarest roles to refill the party is the opposite of a SR. So...I laugh at your logic, or lack thereof.