There are a Myriad of ways to counter her, while she is a popular pick and in Draft people do ban her, there are other champions that would be 'closer' to ruining Dominion or are flat out not fun to play against, though there are strategies for these champions as well.

Off the top of my head: Rammus, Shaco, Kassadin, Singed, Jax, Kog'maw.

Are a few of the champions that REALLY bring the pain in Dominion perhaps as much or more than Akali.

ITT: Akali fan club downvoting OP and saying "lol get Oracle/Sweeper" when no one on the face of the earth ever complains about her stealth.

I'll tell you what ruins dominion for me, its the constant whining about champs and trash talking from people that are not smart players or are oblivious to the strategies of the the game. Learn to play more than one champ, learn to build more than cookie cutter glass cannon, or play a counter if it bothers you that much. Or you could stop playing, stop complaining, and everyone wins?