It's really not a problem in 3v3. I mean you can literally just run away, you have the entire map almost to yourself. Or you can use a super that's quick at shutting down supers, like Striker, Novabomb or GG/Nightstalker. It's not hard to fire off two rounds of GG before a Sunbreaker notices you or has a chance to fight back. And Nightstalkers can just run around a corner, shoot a quick SS at the ground then continue running whilst the Sunbreaker turns the corner then gets caught in the SS. Sunbreakers really aren't the problem, you're play style is.