I think Axebane Guardian should probably be replace with something on the side board. By my count I think you had 3 defenders. I probably would run it unless you had at least ten.

And maybe some ramp for that Avg CMC:

early ramp with color fixing: Cultivate

late ramp with color fixing: Boundless Realms

I realize they aren't permanents for primal surge, but I think some ramp would make your deck more consistent.

Yeah I was just running Axebane Guardian as another means to grab any color mana. I am not relying on the additional mana from extra defenders but if I find better mana creatures I can sub some things out.

I think I definitely need Boundless Realms in there, which is fine with Primal Surge because I need some non-permanents to stop the surge before I mill myself.

Thanks for the feedback!

For clarity you can stop the Primal Surge at any time. The card you stop on remains exiled though.

Mana producing creatures that might work here:Utopia Tree Verdant Eidolon Viridian Acolyte Alloy Myr Opaline Unicorn

Other mana sources that might work here:Druids' Repository (I really like that one) Carpet of Flowers