Amount of ARAM accounts keeps growing
If you have a high MMR in ARAM (you can check this site https://euw.whatismymmr.com/dr%20poro ), you have likely encountered many ARAM accounts. These are people who make a new account just for ARAM and only buy the strongest champions to maximize their chances of getting an OP champion. A second problem with ARAM is that people dodge whenever they get a bad champion or team comp because they expect their opponents to have at least 3 OP champs.
Results? You'll keep seeing the same champions over and over in a game mode that is supposed to be ALL RANDOM
How to fix it? ARAM accounts: Use the entire champion pool to pick a champ from. This also allows you to trade with anyone in your team without requiring eachothers champs. It also allows people to get to learn champions in a faster environment than Summoner's Rift where you're stuck for 20+ minutes if you're doing poorly. Dodging: Increase the penalty for dodging in ARAM. Preferably use a mode-specific restriction, for example a 1 day or 1 week restriction from ARAM games when you dodge repetitively (not for first time/occasional dodges).
Here's a poll. It's not mine but it has a big sample size already: http://www.pvpdatabase.com/?p=1253
and
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. Then there are a few other champs that are just too good in other stuff:
with his heals and insane engage, cc and immunity and
with her insane heals and team auras (she's like Soraka, but more).

. If ever there was a completely retard-proof champion for ARAM, it's that asshole.