Champs that suck on SR can be pretty good in Dominion, this scores major points.
Also highlights those in need of a real look, like Karma, who sucks on both maps.
Not to mention better IP/min, exciting team fights right out of the gate, more interesting items, no need for a dedicated jungler, etc.
Many of my problems with League of Legends (spammy, too much farm, simplistic items) actually contribute to the fun of Dominion, which is basically Arathi Basin where you don't have to grind for a week.