Hey! I just hit Empowered monos and have a similar build overall to what you've got going on here. I'm going to steal borrow some of your ideas , but also wanted to pick your brain on something!
I don't use axes. I don't think it's worth it, but it's hard for me to say that because the mechanics of the game as of yet are very unclear. From what I'm seeing, axes represent quite a bit of flat spell damage (+15 from primalist tree, and 60 from Tempest Weapon in Gathering Storm tree) but I don't see the upside overall. There's a good chance I'm missing something- my 20 hours is a whole lot fewer than 500 hours!
That said, I use a unique wand (Wrongwarp) which grants a bonkers 3% spell damage per 1% movespeed (With your setup, you're around 102% movespeed from boots + haste + stormrider, so 308% spell damage from a onehander, nevermind LP) and the wand comes with 50-60 spell damage on it as-is. With that as the point of comparison it's hard to justify moving to axes, unless I just don't understand how the mechanics work. Are you actually getting +100 spell damage from using axes somehow, or is it just a balance between getting +80 melee damage and +60 spell damage that amounts to more damage overall?
Obviously in using a wand, what I'm missing out on in that is actual melee damage scaling, but I guess I have a hard time feeling how much of a part of the build's damage that actually is.
Also - to complete my mage roleplay I'm using Fragment of the Enigma (Unique catalyst) in the offhand, as its proc scales off of a lot of what we've got going on and can proc off our umpteen lightning bolts. I'm also curious to hear your thoughts on this!
Otherwise, thanks for the guide - I appreciate how much work it is to sit down and write all this up, nevermind thinking through the build in the first place. Cheers!