Alone, they're useless, insignificant and weak; but, when they're grouped up, they can make the difference in a game; in fact, they're an essential element to the game.
My one complaint about dominion is how minions seem to make very little long term differences. In SR they determine the flow of the game, and are important from laning until the final push on the nexus. However, in Dominion, it's as if their presence doesn't make a difference. I'm referring to how minions only spawn at friendly points adjacent to an enemy point and how after minions capture a point, they commit suicide, making wave pushing completely pointless. (Imagine it as if minions suddenly died upon destroying the enemy inhibitor in their lane) Rather than being a nuisance on Dominion, players should have to not only focus on capture points and enemy champions but the minion waves as well.
TL DR: Minions accomplish very little in Dominion, unlike SR
my proposed changes: Minions don't suicide upon capturing a point. All friendly capture points spawn minions every x seconds. Lower frequency of minion spawns. Reduced damage to champions.