I really don't think that they need to nerf him.  I mean he really is the weakest leader late game.  Although the arbiter can rape just about any covenant army (although there are also several groups that the arbiter has a hard time with) he does not stand a chance against literally any army of the UNSC.  Heck, he even has problems killing fully upgraded, locked-down cobras since they have so much health. 

Please do not nerf the arbiter, focus on the real covy issue, wraiths.  Give them a buff!!!!

I'm on your wagon OP!