A one-shot build would work like this, as an example:

2 Maarselok
5 Deadlands Assassin
5 Ashen Grip (Front bar Dual Wield)
Vateshran BACK BAR

You would run this on a Stamsorc. You cast Crystal weapon, then medium attack into whirlwind on your front bar. You would proc cyrstal weapon, Maarselok, Deadlands Assassin, Ashen Grip and Vateshran 2H at the same time directly followed by a whirlwind.

I don't think Vateshran 2H is OP in such a "one-shot build". It is this very combination which makes it strong. I've seen a similar build with Malacath instead of Maarselok. (Maarselok might proc instantly, but the damage actually hits one second later, so it doesn't add to the first burst.) Why would you pick out Vateshran 2h?

Vateshran 2H alone won't let you one-shot anything.

Also keep in mind you need to be in combat to collect the stacks and your skills need to hit something. Vigor works always, but when I use Noxious Breath for example I actually need to hit something to increase my Vateshran stacks. This is not stated in the tool tip and might be a bug.

If you want to see more versatility, other options would actually need a buff instead of a nerf to Vateshran 2h.