Surviving Endgame

So, to try and pull melee usefulness out of the Kripp thread. I was curious about thoughts on life steal or life on hit in this game. In D3 it was a joke trying to move onto inferno difficulty without some decent sustain, usually in the form of life on hit. I'm wondering if that is going to be the case with PoE. Currently, as I understand it, life steal acts like a heal over time unless you get the passive to make it instantaneous. Is this the most logical choice?

P.S. I don't really care about dealing with desync and hopefully it won't have relevance in the future of PoE. Pretend it doesn't exist, for the sake of theory crafting.

Unlike to Diablo lifesteal actually scales much better than life on hit in this game the only major problem with lifesteal is - like you've mentioned - the fact that its a heal over time.

With a marauder i tend to pick up Vaal Pact as long as its not detouring me from what I am going for, the Keystone makes Lifesteal viable and adds quite a bit of survivability.
Without Vaal Pact however i tend to get a Life on Hit simply because its applied instantly.

While both of the above mentioned are decent to have none i really required for survivability in end game, it just makes life a lot easier.