First Double Stealths are Terrible. Why? Anyone with half a brain buys wards, and shuts you down hard.
Anyway, teams I found great....
Pantheon/Eve-His jump strike, Her stun, to his E is just too much damage.
Sion/Singed-Stun, Fling, Poison, Huge damage. Then Poison can help Sion get easy last hits.
Ashe/Anivia- Ashe can Proc Frost Bite effect enough said.
Fiddlesticks/Kayle- Once they hit 6 no one is safe, but her slow works well with his Heal.
Morgana/Nasus- Slow,Stun, Double AOE damage. Both their ults work well together too.