Blizz needs to fix M+ leavers still getting rewards

I've had this happen in two separate occasions now where a toxic party member will ditch at the final boss to "give everyone a lesson".

I just ran a +10 Stonevault with a guildie tank returning to WoW with everything going relatively smooth aside from a few deaths happening throughout the dungeon. The healer, however, would not stop yapping everytime it happened about how they "hate pugs" and "don't explain mechanics to me if you cant avoid them" (I told them not to break all spikes on eden), etc etc. But, everyone just kind of ignored her.

As we near the end, we wiped at the pack at the last boss. Can't remember exactly what caused it, but it wasn't a full reset and we still got through relatively quickly with 6 or 7min on the timer, all dps over 1.4mil overall, and maybe 12 or so deaths overall.

Right before we started the boss, she chimes in "it's hilarious that all of you died purely to mechanics and not to a lack of healing whatsoever", where I finally told them to stfu. Then she left, and proceeded to start whispering me. "This is for you etc etc". Low and behold, we kill the boss without the healer,

We kill the boss nonetheless without her, mainly thanks to the tank, but I know she still got that M+ rating and probably a piece in the mailbox.

Thanks for coming to my TED talk.

tldr: toxic healer left group at last boss and still gets rewarded for toxic behaviour when group kills boss.