When there's ranged vs. melee, the melees needs to go super agressive. Xerath and Vel'Koz? None of them got any mobility to speak of. And Lux is squishy as can be, as well as Xerath and Vel'Koz. And in your example, the ranged team got 2 gapclosers. And Rammus vs Yi (or even against Irelia's stun)? I won't even comment on that.
I'd put my money on the tanky melee's, if there was any skill to speak of on that team.
I've heard the expression "ELO doesn't matter in ARAM"...but it bloody well does. I've had Xerath's for breakfast playing a melee champion, and I've known I'd be dead within 5 seconds if I saw him (he was Diamond 1, so I had to grant him a huge skill advantage).
But as in every other mode, teamwork™ is also essential in ARAM to win, as well as the random luck factor in the champion picks.
I play alot of ARAM (2100 wins or thereabout), and while I try my best in every match, I play not really caring whether we win or lose. It's playing with a detached care modul that makes ARAM...fun, regardless of matchups.
However, there is one thing about ARAM that makes me edgy: the leavers! And I'll have to make a rant of it, but how hard is it really to just suck it up and play, regardless of which champion one gets? If someone can't handle a random champion, which they know full well when selecting the mode, why queing up for ARAM at all?
I once got Shen there - he was F2P, I've never played him before, I could not trade and I had no rolls..so what did I do? I said in the main chat "first time Shen", and tried to make the most of it. I asked for advice regarding build, which abilitiy to max first, what to do and how to play him when I needed some tips.
We lost, obviously - and while the "worst shen ever"-comment was wounding, I just reported the douche - but just appreciated the experience with Shen (and the knowledge that Shen was not a champion for me - which saved me some IP), and not really caring that we lost an ARAM game.