That's odd.
I regularly run mine at .75 ohms and 3 volts when I use a Russian or Kayfun.
I would lean towards the Provari, and if I was replacing it, I would do something better than the VaporShark.
Not that it's a bad unit at all, it's just that there are other box mods out there that are more powerful than the VaporShark for the same price.
It really comes down to what you want to do - to me, 30 watts isn't enough to drip on, and I have no need for more than 12 watts if I am running with a Kayfun, Spheriod or Expromiser.
Same with my DID or Z-Atty.
Maybe my Kraken