So we're all kind of in an odd spot because balancing for Dominion isn't really all that existent. I'm not sure if this was brought up in the past, but why not just bring in more item variants? Right now the item variants are only there to keep pace with the game type. The Sanguine Blade replaced the Bloodthrister because farming obviously isn't the focus of Dominion. So what if we were to apply the usage of variants for balancing?
One example is cutting the popular Frozen Heart and replacing it with a different item. Perhaps an item that keeps the attack speed slow, but has less armor (say 50 armor instead of 99). I'm pretty sure that was a crappy suggestion but, hey, it's an example.
Just cutting or replacing some items may be able to bring a decent amount of balance to Dominion without having to worry about champion balance as much. Of course I'm sure this would bring in a new slew of issues, but I don't want to think that far ahead.