I can prove it to you -- it's not. Don't gear for something that is meaningless on end game mobs. If you want to double-VIT an axe to get crit on body, and that can maintain stat caps, go for it. I guess the logic there would be "better to have it than not have it", but the numbers don't really show it being all that great of an improvement. The trade off is rather poor too. To pull off VIT melds you'll be dealing with a crafted axe, all of which are vastly inferior to primal/GC weapons available. Will your crits hit hard? Yes. Will you increase your DPS by doing so? No, for the reason I just stated. Check it:

Best axe available is Barbarian's Bardiche, and hey it already has VIT+5 on it! Leg-up there... but it's DMG is 151 and 35.95 DPS (LOL). Or you get Garuda's Scream, which not only has 8 more base damage (and DPS: 40.76), but also has Accuracy, and Critical Hit Attack Power +40 (you wanted this, right?). Look at the math and ask yourself if that is worth it. I don't think it is.

Gearing in this game is actually a lot simpler than people think.