As Vy just said:
Wouldn’t it be easier to just… you know… remove the depletion mechanic?
The only reason why leaving is such a big issue is because the key actually gets depleted.
If keys wouldn’t get depleted the damage done would be significantly lower and most people would probably not even care and just “go agane”.
Furtheremore, Pugging already has the issue of tank/healer shortages. This might even further disincentivise tanks/healers to PuG and the waiting time will get longer.