So what you mean is basically that a 5-stack will have to win - what - 65%+ of their games to rank up at all? Because this is what I would assume to be "ineffective".
Also, as a D2, does that mean that I can play against 5-stacks as a solo player? And is it possible now, before the patch? I thought it didn't happen usually.
Unlucky, really.
It's very rare for 5 stacks to not be put against 5 stacks in our current system(but it does happen). Now the system won't be able to do 4+1 because we aren't allowing for stacking, so it should reduce it even more to how much you run into a 5 stack as a solo player.
In diamond3+ if players 5 stack they will only play other 5 stacks as well.