I have a radical suggestion: No secondary school! I have a balance at level 45 who is pure balance, no secondary spells at all. I generally solo and have had no problem so far, including the first parts of DS. Maybe it will get harder as I go through DS but so far so good.
My main reason for no secondary school is that I am waiting for Celestia. Since balance has such a wide variety of spells, I figure whatever spells Celstia has to offer will probably fit in.
If you are set on having a secondary school, I would recommend death to Feint. Justice is strong with a 70% increase would really hit hard! Also, probably take life to Satyr. Helping hands is good but can't heal someone who has died already. Balance really has no need for Tower shield given all it's excellent shields. And personally I don't think any school should attack with spells outside their school (this is even more important when you get to Dragonspyre).
Hope that helps. Balance is a great school so enjoy!
