I'll give my 2 cents until Archi can come in with a concrete answer.
1.) ER/DT/Av/FC or Warpaint/Carn/IR/DR. War Machine is extremely good when you can keep high uptime on it, such as dungeons. Its usefulness in raids will be determined on how much uptime you can have on it. Frenzy is probably about equal to Inner Rage now for single target since the RB nerf, but I'll need to see official numbers first.
2.) WM or ER/DT/WB/FC or Warpaint/Carn/IR/BS or DR. Once again, War Machine is extremely good when you can keep high uptime on it, so you will use it any time you can do that. The main choice here comes down to Dragon Roar vs Bladestorm, where Dragon Roar will probably be stronger for frequent burst Aoe and Bladestorm being stronger for infrequent burst AoE without too much delaying Bladestorm usage.
3.)
http://legion.wowhead.com/artifact-c...PhAz4wM-QDVNAQ is the most optimal path getting you to your major traits the quickest. I believe Rage of the valarjar is the highest DPS increase so get that first then work toward Odyn's Champion.
4.) Sarri has some for Arms, and I believe Archi is working on some for Fury, or will in the future if not already.