Arbiter should have gone hunters and locusts. Send the hunters in while keeping the locusts far. It is even more difficult to stop this combo when they have a couple of cobras with them. For the UNSC, Cobras and scorpion tanks. Drop the ODST once in combat and try to have the marines rocket the tanks and wolves in an individual manner.
Ronin 3003:Practice raging tanks in private games. If you can't rage full pop tanks w/ a T1 arby, it means you are worse than klunk and should consider using a different leader. =/