its risky for sure but if you follow a sucide grut or brute rush up with some banshes they wont have a leg to stand on. The Covenant have no other opitions but to go air hunters suck because I can simply canny glitch an army of them away wraiths get destroyed by PT tanks and all the rest of the units are useless.
I personally play UNSC because of how useless the Covenant are in a long game.