Necro with warfare is actually fantastic, due to warfare multiplying physical damage, and necro is largely physical.
For casters, shields are most certainly not useless. They are a great source of armor for squishies. If you are using your off hand on casters for something like a wand, you are spending your action points inefficiently.
Your builds look reasonable, I would agree with seb however that summoning can get boring if you don't take a variety of summons. dropping down some of that Geo to pick up other elemental / summoning books might be more fun.
