Disclaimer: There are a ton of variations on this build and I don't have enough under-the-hood knowledge of the D2R engine to say that mine is the best, but I can explain why I like it. I'd be glad to get any feedback, as there are lots of game mechanics I could stand to learn about.
Primary Skills:
Secondary skills:
* Why not more in fire? First, Phoenix Strike meteors are known to cause disconnects so I avoid using them. Second, Fists of Fire has a hidden effect of converting a percentage of your physical damage to fire damage (% = skill level * 3). That isn't necessarily bad, but at or over 100% that will mean no physical damage for leeching.
** Tiger Strike is a viable alternative to Dragon Talon for spare points, and will give a better physical damage bonus, but I have to think the extra strikes from Dragon Talon outpace this especially considering crushing blow effects.
Passives and Prerequisites:
First off, Mosaic makes this a late-game build only. You could play martial arts from the start, but before mosaic it's a whole other discussion. If you haven't played mosaic before, let me also prepare you for a polarizing experience. The benefits are extreme, and so are the annoyances if they bother you.
Benefits:
Stuff you might hate:
Attributes:
Standard stuff, str and dex are whatever you have to invest for gear, the rest into vitality.
Gear:
Two mosaic claws are mandatory, but a lot can be said about what bases to use. The very best skill mods for improving damage are PS, CoT and BoI. Fade may be good if its enough to be better than your +skills on switch. You can save a skill point if your claws provide Shadow Warrior or Mind Blast, and Dragon Flight will save you three, considering its two needless prerequisites.
I avoid superior bases as they can make repair costs high. Damage on the claws is immaterial--while attacking with your claws you aren't trying to kill, you're trying to charge up so it's actually better if things don't die from it. Attack speed for your main hand claw matters, but again only while charging up so even that isn't super important.
IMO, amazing skiller claw bases are for people with a mule just for Jah runes. If that's you, great. If it isn't, don't sweat it. With or without skill bonuses you will live a Superman/Clark-Kent life depending on whether your charges are up. Better skills make a stronger, faster superman, sure, but without you just have to settle for invincibility and the ability to shred everything short of Uber Tristram without a thought to its defenses.
Other stuff you want from gear:
Cobra strike gives all the leech you could ever need (if leech works at all, depends on the enemy), and attack rating only matters while charging up--charged kicks always hit, like smites. Faster attack speed matters, but because of Next Hit Delay it won't improve damage from Phoenix Strike or Claws of Thunder, so it's optional. Things that improve physical damage are also good (i.e. better boot damage), but with crushing blow from Gore Rider or another source you'll easily put down things that have to be killed with physical damage (if not terribly quickly).
For Uber Tristram, Dracul's Grasp is mandatory. Apparently, life tap works even on things that are immune to leeching (as all the Uber Tristram bosses are).
Fighting tactics:
With charges up, you push the kick button until everything is dead. We don't need to talk too much about that.
Cloak of Shadows is an MVP skill when your charges are down. It adds to your defense, subtracts from theirs, but even better it encourages them to stand around not killing you. Shadow Warrior makes a nice distraction, and since she only uses skills you currently have selected you can encourage her to use Cloak of Shadows often herself. Mind blast is a spammable 3rd option when the first two have been used.
Plan on using fade most of the time. Given that most of your ideal gear has no resists at all (claws, Enigma, Shako, String or Arachnid, Gore Rider) you're almost certain to need some help there from fade, but even if you don't the physical damage and curse reduction would still edge out the benefits from Burst of Speed, IMO. Burst however remains an excellent in-town and between-fight accelerator.
This is what a typical fight is like. Prep with a Shadow Warrior and Fade. Approach enemies and use Cloak of Shadows. Begin charge-ups: 3x Cobra Strike, 3x Tiger Strike, 3x Blades of Ice, Kick (to refresh timers). 3x Claws of Thunder, 3x Fists of Fire, 2x Phoenix Strike, Kick. Kick until everything everywhere is dead. In my experience, even a very well geared merc has a tough time surviving the charge up phase (maybe a rogue would do better?), but nothing a merc would provide is crucial for this build.
The biggest thing I've taken away from my time with this build is this: you don't have to make the superman stronger. If your charges are up, you are superman and you win the fight, period. Winning faster is great, but if you are losing fights it is probably because it takes too long to find the next enemies to kick. That makes run speed a top-shelf gear mod, along with resists, physical damage reduction, and defense.
Edit: I use the Superman/Clark-Kent reference not as a snub to Supergirl, but because Kara Danvers does not evoke the sense of fragile uselessness the metaphor requires. Respect.