I think the small group of summons should be the Druid Summoner's schtick, where the Skelemancer gets a huge army and the Golemancer should get one absolutely beastly summon. To that end, I think you should only get one Golem - but it should get all four things combined. Plus a huge damage increase, because it desperately needs one.
As for my own top choice, definitely skill fixes. Rebalances and bug fixing.