I have a list of skill synergy suggestion here. I added my thought about skill changes that go with those synergies.
For summoning skills I think
Cold mages should be removed be they can explode bodies
Golem skill should increase their base damage not off weapon bonus
Golem attack speed should be quicker
Revives instead of a time limit should have drain % max life effect instead and points into revive reduces this drain life effect to a minimum value. This way life tap is basically a synergy because it will make your revives live longer.