Whenever we go into a match where the other team is ganking we have always won. If 3 or 4 people are on 1 point then there not on the other two. It's more challenging on smaller maps but we still win. Ganking is agitating but it's not a winning strategy, and if you have a good tank on your squad then it's even easier.
Eh, most people have figured out 2v1's now; either GB, or wait til the outnumbered player is attacking, then hit from behind. A well coordinated gank squad will kill you in 5 seconds flat with little difficulty, then run as a group to the next point, repeat ad infinitum. It's definitely an effective strategy when performed well.