This might help you. (Coming from the man Legendspimp himself)
Posted by: nickyfour92
What would be a good strat for getting a flag cap on Onslaught? Such as when to move in, where to cover for the flag guys run, and how to predict which corner (A or B) of the base they will spawn.
If you could PM the answer that would be great.
Well, before even attempting to go for the flag, make sure at least three players on the opposing team are dead ( and know where the last player is so you can isolate and kill him.) The enemies will only respawn A side, B side or on the flag. Immediately after grabbing the flag, most likely they will respawn A side of B side because the flag player is choking the respawns in the base itself. You can prenade the A side or B side if you DO NOT want your opponent's to respawn there. The reason this occurs is because grenades "choke" respawns or cause them to not respawn in that area. So you can now anticipate where the respawn's from your opponent's will be with that knowledge.
I recommend staying up top while attempting to cap a flag, typically as high as you can be with a view of both A side and B side of the opponent's base. Make sure your teammates are very good with communication so that when your opponent's do respawn the first player to acknowledge the enemies can inform his teammates. Remember to jump and look upward (tossing the flag) to get a maximum distance on the throw. Never try and go in the front of the base due to the open vulnerability to becoming shot/grenaded.
Usually after capping the flag you need to play strong defense and most of the time your opponent's have killed most of you in the process of you scoring that flag( unless of course your an amazing team with amazing accuracy.)