Warlords bloodlust and skarner

would it be viable?

I don't think so. You're probably thinking about Skarner because he has low cooldown AoE damage on his spells, but I'll be the first to point out that spells aren't affected by Lifesteal, only basic attacks. It might help his early clear because he's using tons of basic attacks during that, but that's really it. If you're basic attacking enough in teamfights to use the new Warlord's Bloodlust, you're doing it wrong. I say that the best mastery for him, and most other junglers, is Strength of the Ages. Get tankier for later fights and early ganks, plus it helps your clear and you can stack it off of jungle monsters.

Terribad, why?

Why would take it over Grasp or Strength of Ages?

i just figured it might give him more sustain in team fights esp since most ppl seem to be building AS on him like rageblade and wits end

You really should be taking strength of the ages especially on junglers with HP scaling shields. Skarner doesn't deal enough raw rightclick damage to warrant warlords anyways.

would a hextech gunblade be any good to use on him since his Q is on sucha low CD?