What difficulty are you playing? If on Classic, it's not that important to optimize anything, if on Tactician, your fault. You can respec the companions after Act 1 on the Lady Vengeance, so no need to plan for the endgame already.
Do you want a mixed damage group or focus on one damage? Later on some enemies have huge amounts of one armor while lacking in the other. I have a mainly physical damage group, sometimes it would be much easier to fight the magical armor on some enemies.
Your battlemage is already of mixed damage, so that may be the way. Ranger, Wizard and Summoner would be my choice. The incarnate can tank to a certain amount and you have high damage against both armors.
You can also create a kind of polymorph control tank (Medusa Head f.e.) out of your battlemage but then you should concentrate against physical armor. The problem is a certain lack of support/healing skills. You have one physical armor restore from Polymorph, but that's not enough. Geomancer and Hydrosophist offer some great armor refresh possibilities, more important than vitality heals in my opinion. You could put it on your ranger and summoner and wizard.
I have respecced my Necro/Hydro/Poly/Warfare shield and board main into a Warfare/Geo/Hydro/Poly combi. Necro went to my two-handed warrior. I would not like to be without certain Warfare control skills as a melee.