I think he might be looking for something that benefits from both Ao and Iruka's shields - so a water or fire main.
Yeah it would be better but the team that he suggested is also good Ao will use shield on 4 of 6 possible targets and Iruka will boost everyone except Ao. And Aasuke with his mistery will boost even more the midnight blade.
Also, a point to note would be that it's actually pretty hard to find a solid lineup with Ao if your main is fire/water. Believe me, I've tried. Ao only really becomes useful for those mains when Kage Treasure comes out. Mei ftw :P
Are you sure there is no way to use both ao and iruka in same team with water main? If so, which one fits better and with ninjas? Now i am using Sasuke, iruka, kiba gnw and main.