How can I improve my Storm Rain build for uber bossing?

Hi everyone, I just finished with a project I had for while, which was to create a build that does not use anything crazy (sub 20div) gear and can do ubers.

This is what use to map:
https://pobb.in/RgbKrmP32ke9
*please ignore the resistances, I had to swap lighting to boost my fire res for Uber exarch.

Main issue was dealing with uber exarch:

1. the ball phase is OK and I could tank some of the hits, the problem was the runes even with a huge net recovery I would die quicker than I could react.
2. The annihilation skill, I can get 88 or 90 res with a swap in the jewels, but even with 15k net recover and 4k HP+1.2k ES I still died constantly with a few of the shots, even when I was stun immune.

So, question is there an easy way to get 20-40% more dmg without crazy gear? But keeping most of the defenses as it is? I did not try going deadeye, this build has a more damage, but pathfinder solves regen pretty easily for me.

Or could I make it tanker against phys and fire without losing the damage that I have?

PS: to clarify I was able to kill uber exarch, used a enchant ruby flask (for res), and an enchanted quicksilver for the fire salvo, but mostly using all portals, where for other ubers the fight was much easier. Maybe it is just how the fight is. I dunno you guys tell me.