What's the thermal conductivity of adamantium anyway? How quickly would the lightsaber's heat spread to the rest of his skeleton and cook the Wolverine from inside? Inconel's tough, and it's under 20% the conductivity as pure iron; it'd be a pretty good analog for adamantium. Unfortunately it's got a melting point of around 1400oC, compared to the alternative of tungsten carbide. That won't melt until twice that temperature, impressively enough, and won't boil until you hit six thousand. Tungsten carbide is also really tough, but it's about 160% as thermally conductive so it would end up with a faster self-cooking superhero.
Of course, none of that matters; plasma arcs start around eight thousand degrees celsius and go north of twenty; the general opinion that 'Wolverine's screwed' is quite accurate. Can a lightsaber kill Wolverine fast enough to make sure his regeneration doesn't save him? Likely, but that depends on just how fast he regenerates - and that's a factor of caloric energy, organic chemistry processes, and the question of 'minimum quantity of Wolverine required for a regenerative seed' as well.
I think about weird, weird things listening to VNV Nation at one in the morning...
