What is a good # of armor to aim for with 2H builds?

Reached to a point with my marauder where the main dps, utility and ehp nodes have been picked up already, I don't however have any armor nodes yet. I do have pretty solid HP pool which will only get bigger as I add more HP into the gear, but my armor is currently pretty low despite me running determination aura (but not using iron reflexes and grace). Now, one of the main reasons for that is that my chest has only 700 armor on it, so once I replace it with 1500-2000 armor plate I think it'll rise up to more reasonable value, but that still leaves me thinking; should I still go for more via armor% nodes?

I use mainly ground slam for ranged/aoe damage with about 3k dps and for single targets I have glacial hammer with about 6k dps, both spells will be getting more damage once I get 5 link weapon & chest. So I am not that worried about the damage, but armor is something I am curious about and would love to hear how much armor 2h maras bitween level 70 and 90 and rolling with. Would say... 5k armor be fine as long as my hp pool is sufficient? Or should I do some more serious investment on armor nodes in order to push that number closer to 10k?