All these posts about how difficult the gamemode is, are confusing me.. Do you want it to be a 'Try once, easy win' gamemode?
A lot of it has to do with teamwork, and having to try multiple times gives you a chance to improve your tactics and actually think about what you as a team can do to win the gamemode. 2 of my friends and I played it with 2 randoms, and it was a lot of fun. We were busy discussing tactics and assigned roles to each person. We managed to win the first game we tried and then went straight into the 'Onslaught' version which we also won in one go.
I can see why some people can find it difficult, but if you try a few times then I'm sure almost anyone can win the gamemode. Just give it a try again. ^^