Thank you for the input!
I have definitely noticed that weakness to Banished Pantheon recently - the difference between a Knives repeater and a Pantheon repeater has been pretty stark. So I took a bunch of your input and a few odd tweaks to create a "Wishlist" build. Now I just need to figure out how to afford it...
A few notes on other changes:
Switched Ring of Fire to Char. I lose the occasional "quit running," but it was able to accommodate +12% Fire/Cold slotting.
It seemed like there was a whole bunch of stray slots after the recommended changes, so I tried to find any low hanging defensive bonuses I could get.
Switching Irradiated Ground to full Analyze Weakness - this capped out the S/L Defenses. That said, I could move two slots from here to Melt Armor for the buff, and put... whatever I can get a good 4-slot bonus with. I will probably play around here to see what I can do.
Thanks again for pointing me in the right direction - I've got quite a bit of farming ahead of me, it looks like. At least the in-progress build has been fun for that part!