I’m not sure… Mortars are not like Devils, Box or TSS. On a classic no-wpn dmg caster you kite freely while your casts do the work or kite with stops for nukes. On Mortars you gotta keep them stationary meaning you gotta facetank. And you can’t facetank without sustain no matter your defense.
Getting energy regen as your primary source of sustain is and always will be too expensive. Using Ghoul and adcth with some Stormfire is poor because you don’t deal enough weapon dmg. The only way is procs (Bat, Reign of Fire and Ice Rings, the new Bane relic, Ulzuin Wrath is also good) but its also limited.
My suggestion for Pyran would be to give some solid support for Ulzuin Wrath (+ranks, flat dmg mods or +%adcth mods). Phys res and scraps of extra health regen are nice but aren’t even close to making up for the lost dmg.