This is possibly the most straightforward poke to use I've ever seen. Can't set up and sweep, can't use any worthwhile support moves. It literally can't do anything worthwhile other than a set with four attacks on it, and at this rate it appears like it's probably going to be the same four moves almost all the time - you're guaranteed to be using Water Pulse, Dark Pulse and Aura Sphere, and it looks like Ice Beam is going to be the preferred option 90% of the time over Dragon Pulse - although, I actually have Sludge Bomb on mine in that slot, because every other choice leaves you hard-walled by Azumarill. You still get most of the Grass types that way, although you do miss out on quite a lot of damage against certain Dragon types - Salamence, Dragonite, Garchomp, Dragalge and Goodra in particular, although you can still hit them neutrally for fairly solid damage with your other three moves. Hydreigon, Kyurem and the Latis all get hit plenty hard by Aura Sphere and Dark Pulse.
Its EV spread and nature ought to be pretty simple to figure out too - you obviously want to dump 252 EVs into Sp. Atk no matter what, and the remaining 252 probably want to go into HP. Speed is awful so it's not worth bothering with, Attack is too low to bother with also despite Swords Dance. Nature is probably going to be Modest 90% of the time, although there's a small chance of Bold or Calm if you want to buff his survivability a little.
The only real rub when speccing this guy out is the question of what item you use. Do you use Choice Specs and risk locking yourself in, when Clawitzer's main selling point is his great coverage? Is Life Orb's damage boost worth eroding his bulk away? Does it hit Super Effectively often enough to warrant Expert Belt? Perhaps it wants Assault Vest or Leftovers to boost its longevity, but will it have the firepower necessary with no boosting item? In the end, it doesn't actually seem to matter all that much, as his role stays the same no matter which one you use - take hits and fire back. I actually think one decent option not yet mentioned might be a Focus Sash, so you can use him as a utility check to runaway sweepers.