You dont get a penalty if two people have left the mission, I know because one day it was simple horrible with disconnects and de-grouping and 2-3 we had to leave because that mission became impossible to complete.
That may be how it's SUPPOSED to work. Reality is something else though.
If cryptic got finally their act together and someone leaving would instantly be replaced by another player the whole leaver penalty would be unnecessary.
As someone who has been "drafted" into half finished STF's where the optional has already failed and now filled with people flying about not sure what to do ... I hate your idea. How about you not quit and stick it out in the pug group you started with and finish something you started.
I get into alot of groups where theres one guy in the group with the "you newbs suck" attitude and I have to tell you, 99.9% of the time the person doing the most complaining has not once stepped forward to take a leadership role. Instead they just drop group and go back to DS9 or whereever and complain in zone chat.
Grow up, grow a pair and lead. or else go play something else.