There are better options for a defensive 'mon. Yes, his defensive stats are very impressive, but he has no recovery options. He can't even use Rest or stall for Leftovers recovery with Protect. He's also vulnerable to all entry hazards and Toxic.
Really, the most you can do with him is annoy your opponent with ParaFusion + Knock Off in the hopes of stalling out Slow Start. He just can't do anything else.
I'm not sure. I suppose your right, there might not be anything better in NU, but big stats aren't everything when you have very little to back them up. While he may have few weaknesses, he has little in the way of resistances either, and there are still plenty of things that hit fairly hard in NU. Add that on to no recovery and I still can't see him walling much.
With a little hax, and its 110 - 110 - 110 defences, you only have to use TW and Dizzy Punch. After 5 turns you have a fucking Jolly monster with 419 Atk and 328 Spd!! Is a sort of glass cannon, yes, but not like Rampardos or SlakingBut you can at least kill something with Truant >.>