Need advice on my build

Looking for some tips on what to change next as I've been struggling for a while now (starting act 3 cruel).
Here is the gear and passive tree of my lvl 51 marauder. Thanks in advance.





Edit:
My mana is ok, my biggest problems are low dps and life, I can't really do much damage and die very quickly when fighting boss/a group of mobs.
My elemental ress are decent I think, my chaos ress really isn't.

Edit:
Made a few suggested changes, it's going much better now, Thanks again

You have focused to much on damage but forgot survivability, you should probably get more health nodes, you can get damage from your skills, and you will actually survive long enough to kill bosses.

I would also consider getting blood magic in order to use more skills and have 3 health and 2 granite

And getting more endurance charges (and using them if you are not) would help you a lot

You might have to respec some point out of some damage passives and putting them in survivability

I hope this helps

(this is what would help your skills though you could probably focus more on what you need for your specific build)

Sure it helps, Thanks for the advice.
But I do have some doubts about blood magic and endurance charges, does my life increases with blood magic? ie suppose I have 1000 life and 500 mana, with blood magic will my life become 1500?
And I'm not very sure how endurance charges work, afaik they are only useful with some skills, I'm I wrong?