Tank.
I'm tired of loosing matches because no one wants to tank, and it's just "aram." In a situation of 5v5 the person who initiates is gonna poof. You can't do any damage if your dead at the start of a team fight. So if you get stuck with thresh and you have a yi and a quinn on your team, then dont go ADC thresh......we need a tank or else you will loose a 4v5 because the 4 team has a balanced build and the 5 are all greedy damage whores.
Get over it, it's ARAM. I frankly couldn't care less if I win on ARAM, I just find it to be a stupid fun map to try weird things on.
"Random" means it will never ever be balanced, whether you win or lose is most of the time decided by champ select.
I think you're forgetting the real secrets to winning on ARAM: 
Sorry if I want to win my games. Unconventional builds are welcome in ARAM to me, but that is not what happens. 75% of people think "hey, you know what would be cool, AP Alistair etc..." So what happens is EVERYONE tries to be the damage dealer. Sometimes you might need that Maokai to play carry, BUT someone is gonna have to tank. There needs to be a strategy other than "how can I get more kills than my teammates." It's not fun to loose a match due to greedy champ play and unresponsive builds to the enemy team. There is a difference in "just having fun" and "just not thinking."
But it's All Random All Mid (hence ARAM), what if you do not pull a tank?
you win ARAMs by not playign them
Well ap people can build 
to be tanky
