3.4 Mage Skeleton Necro. Help me tune it for U. Elder?

Let me start off by saying thanks to GGG for Delve. It has its issues, but this is the league that has motivated me most to get through content and push a build. I started in Abyss after a long D3 hiatus, and I've really latched on to this league.

https://www.pathofexile.com/account/view-profile/bruceisbest/characters

(This is my first post here and I'm unsure of how to link everything so I'm sure there will be edits.) BooTangClan is my Skele Mage Necro. I started this build based on a post in this forum, but have since gone a bit rogue with it. For the first time ever I've gotten through Elder and Shaper as well as Delve 300. I tried Uber Elder this morning and got absolutely walked on. I know most of my failure was due to me not being up on all the mechanics; but I got absolutely crumpled by everything except Elder's ice triangles.

I feel like my build has hit it's upper limit, but I also know I'm a relatively new player and this can't be perfectly optimized.

How can I push this build the rest of the way? I've got a few ex at my disposal currently, and I'm not adverse to trying to craft new gear if I have to...

Skelly mages are simply not good at some boss fights. Maybe get a taste of hate flask, swap your gmp and pierce for added cold and slower projectiles. And give up about 10-20 damage nodes for life nodes. You won't dodge all his skills, so you need to survive a hit or two. Or swap the body for a kaoms heart, and put the zombies in a decent elder rare helmet.

Another option: Run as an occultist. The raw defences are much better than necro with the right items: https://pastebin.com/mX7tsZaA

and profane bloom means you can always run with boss gems, the explosions take care of AOE.