Not much experience with multiplayer, but it seems to me that Armenia would be quite competitive (no need to worry about the p-poor starting position and lack of pop growth in homelands). Cat archers are my favourites. In a 1.1 Armenia game I found that I needed nothing else to beat all comers. They didn't kill elephants, but routed them easily enough. Cat archers are kind of a counter-everything unit
Armenia also have decent phalanx and mock legion units.

Having the best archers combined with getting a height advantage is likely to be a game winner. The Egyptians are lethal... they had 9 archers on a hill - I sent a full unit of javelin cav after them (my choices were limited and I needed to sally) - my guys routed before they got to the archers - only half of them returned. Cretin arsers are really really good. Rodeo singers are really good.
Egyptian Metal Skin Mutant Axemen are also too good, but I think someone said they're slightly nerfed in 1.2