One other neat strategy I came up with quite by accident (accidentally placing my infantry in the rear one fight) is to use your comunion slaves as blockers. This can be very useful because they are effected by everything the communion masters cast to buff themselves. That means if you have a large communion with diverse mages, you can have each master cast one of the following:
body ethereal, personal luck, invulnrability, breath of winter, fire shield, astral shield, mistform, etc. etc. Each master (in the back row) is only moderately buffed, but each slave (in the front) is a fairly indestructable linebacker. Obviously you need some way to cope with arrows before your buffs take effect (chaff works well), but I've actually found this is pretty damn effective because the synergy here is that the higher the slave:master ratio is, the longer the masters can keep casting...while also having more effective linebackers (with fire shield, breath of winter, etc. they even have a bite). Not many deaths from fatigue when you've got a 4:1 ratio...
