Mark is ruining ARAM
I don't know if ruining is the word, since ARAM is meant to be whichever team has the better comp has an advantage, but it has shifted so many more champions in to the 'might as well not play' category.
ARAM is not a balanced game mode, to be sure, but the summoner skill mark is making it less so. You can lose an entire game because of 1 or 2 enemy heroes with mark (and it's still an incredibly common summoner skill). Having mark on a hero who already has engage is crazy, amumu (or kat, or galio) being able to perfectly position their ult is game-breaking, and instead of just having to worry about flash / skillshot range now you have to worry about 5 people in a single lane avoiding a spammable skillshot.
The skill needs to be reworked, re-balanced, or removed.