There are a variety of ways to solve the intense mana cost of Rejuvnation or Devouring Totem in a 6-link. The most ideal is generally the Slavedriver's Gloves from Atzoatl which allow you to pay life. Alternately, you can run Eldritch Battery and pay with energy shield. You can even link a Lifetap.

However for Pathfinders, there is another method - massive mana cost reduction. I'm in a small private league and thus the Atzoatl gloves are out of the question. I tried EB a couple different ways and wasn't satisfied with how it felt.

The strategy for mana cost reduction I've used is pure mana cost reduction. I am currently running 6 of these, which gets my mana cost down to about 7 mana where my natural regen can keep up.

1. A flask with 100% uptime crafted with Reduced Duration & Increased Effect. Then craft 25% reduced mana cost of skills onto it. This saves a massive amount, 50% in my build.
2. The Life Mastery for skills cost 30% life instead of mana.
3. Militant Faith timeless jewel with 1% reduced mana cost per 10 devotion. Placed in the socket near PF starting tree position, you get 14% reduction and don't lose anything important.
4. The Mana Mastery for 10% reduced mana cost.
5. Rings/Amulets with "5% reduced cost of skills" and/or "-X mana to non-channeling skill".
6. Rare Jewels with "5% reduced cost of skills."
7. Dreamer (anointed) for 10% reduced mana cost.
8. Watcher's Eye with "-7 to mana costs while affected by Clarity."

Note that currently PoB doesn't properly calculate costs affected by the Life mastery option. It is a little bit off, so verify everything in-game.

For my build's cost reduction I'm running a flask, timeless jewel, life mastery, mana mastery, an amulet with double cost reduction, and one rare jewel. This brings me down to about 9 mana per cast, which I can easily sustain off natural mana regeneration.

So if you don't like designing around energy shield regen, spamming life flasks with zealot's oath, or spending big for the gloves, give this a try!

Current PoB: https://pobb.in/-AhWWOZI653i