It appears as if I have far too much time on my hands because; I have actually given this idea a fair amount of thought. At least as far as producing the most viable Iron Golem that Provides an Aura and, keeping it alive. The problem with making an Iron Golem that could survive almost anything is that it requires quite a bit of wealth. I will not bother to post the particulars to this project because of the drawbacks that will make such a task impractical.
It also requires that a Necromancer be built around this project rather that the Iron Golem just added on later. The Necromancer would of course be almost entirely a Summoner in nature. He would also be limited to PvM because his death would be one of the primary hazards to the Iron Golem.
The Necromancer should also be at about level 90 before, the Iron Golem is raised. This will give you enough skill points to insure that he is viable.
The Iron Golem would only be adding another Aura to your other creatures anyway and, would never be that powerful by itself. The item to make an Iron Golem from presents a problem all in itself. Any weapon tends to make a poor Iron Golem as far as survival is concerned. Even a mid-grade armor will outlast most weapons. This tends to limit some choices right off the bat because, the plain fact of the matter is that the Iron Golem will not survive if made from a weapon.
If made from some kind of good armor there are only 2 major threats to the survival of the Iron Golem. The greatest threat is that you die and, take your Golem with you. The other threat is in letting your Golem be swarmed. This is not a major threat however because of the large amount of life it could have with the correct skill point assignment. You could if needed have time in almost all cases take a quick Portal to town if there was any danger of your Golem dieing. After eliminating weapons as a choice, the choices would come down to; Exile and, Bramble.
Bramble could be nice but, it could just as well be placed on your Mercenary or, yourself to provide the same benefit.
Exile would be the only close to practical choice at this time. It only provides a defensive aura and, it could be somewhat useful but, it has a down side to this choice as well. It has a 15% chance to cast Life Tap when the Iron Golem does strike a monster and, having the curse you are using over-ridden by this could have less than pleasant results.
The best hope to make a viable Iron Golem is in a new Rune-Word with a greater benefit and, less of a down-side. If that should ever happen; I have a plan ready for action.