Personally, I wouldn't spend the tomestone for it unless you can upgrade it to 340 right away.
I've used tomestones on body and belt so far (got savage drops for head&legs) and used crafted right side.
I will probably upgrade my weapon to 340 this week since none of my DPS want to spend the tomestone for the weapon and I don't have much else to spend my creation on.
It'd say it really depends on your raid progression and how geared you are right now.
You don't want to waste 3 weeks worth of tomestones now if you're already well progressed in NeoEX. If you're still in V3S, that might be worth it.