@ineffablebob I loaded your RF build into Path of Building to have a look. These are my notes.
Similar flask buffs don’t stack. Replace one Granite with a Basalt, Quartz, or Jade, especially if you have downtime on the Endurance Charges.
Dousing suffix removes RF. I know it can be a safety measure, but I prefer to be able to mash my flasks. A bigger effective life pool is safer than adding more regen.
I would replace the dousing Granite with Basalt + grounding, and the curing hybrid flask with a Blood of the Karui. Maybe get the poison-immune Pantheon upgrade if you need it, or just bring chaos res + curing when fighting The Hunter.
Molten Shell is more useful & reliable if you don’t CWDT it. I’d use Immortal Call + CWDT + duration and cast MS manually. MS -> Shield Charge (+Fortify support) -> Enduring Cry is a nice combo to initiate with. I didn’t see much charge generation, and Enduring Cry will help if you use IC. I’d keep Flame Dash for mobility/escapes, or replace both mobility skills with Leap Slam. Endurance Charge on Melee Stun is also good with Shield Charge because of the stun threshold bonus.
IC gets more effective the bigger your life/ES pool gets, and the better your endurance charge count and generation is. It’s common to see it on builds with 12k ES and no charges, or doubled up with other guard skills, because of the scaling.
Since RF doesn’t hit, you could drop Wave of Conviction and take Elemental Equilibrium instead. Then remove your hitting fire skills, and get Added Lightning/Cold to trigger EE with Shield Charge for example. I think MS/VMS may interfere with EE, even though it’s reflected damage. Another option for EE is Malachai’s Artifice, so only the socketed gem applies EE.
Flesh and Stone (sand stance) is huge for any (non-blinding, non-evasion capped) melee range character. Add it ASAP.
Vaal Impurity of Fire is splitting souls with your Vaal Molten Shell. I’d drop Impurity and Vitality for Flesh & Stone and Arctic Armour or a Blasphemy curse.
Adding a slow like Arctic Armour, CWDT + Cold Snap, or Blasphemy + Temp Chains can be great. AA is underrated, IMHO.
Always remember that the POB and in-game “physical damage reduction” number is an estimate. DR caps at 90%, but only flat DR sources are reliable. You might not be reaching 90 in bad situations when huge boss hits or crits out-scale your armour. Granite + Basalt + charges will help cover the gaps or downtime in your defenses, even though it looks like having over 90% is wasteful.
Ideally get a Kaom’s Heart, put the RF in a 4L, and drop Efficacy since the More Spell Damage doesn’t help RF. This trades some DOT for +1k life and extra armour. Then your gem setups are something like 3L IC CWDT +duration, another 3L CWDT, 4L RF, 4L Shield Charge, and leftover Flame Dash, VMS, F&S, AA. Maybe use Leap Slam if you want to save a socket for Enduring Cry or Frost Bomb or something else.
My priority would be: swap auras for Flesh & Stone + Arctic Armour, manual MS, new flasks, move skill + Fortify, CWDT IC and charge gen.