Fire sorc is pretty easily the best sorc now when fully slotted out
Blizzard is better for weak gear setups and doing shit farming, I mean you can grind trav with a nearly naked sorc
BiS fire sorc really gets to choose between 10x facets or 2x phoenix or a mix. Giving +50/30/0% fire, -50/58/56% pierce, and 0/80/99.2% chance of 0/95/170 life+mana redeemed per corpse (ev 0/76/169 per corpse per tick)
so in total;
phoenix sword (or 30/30)
phoenix shield (or 20/20)
ormus or vipermagi (defender's fire)
3/20/2 circlet or flickering flame
+2 sorc / 15+ fcr crafted ammy
magefist
soj+opalvein or 2x opalvein
arachs
resist boots
cta/spirit swap
merc with infinity cure coh
Now you can also use a 3/20/2 circlet with 2x facet, and ormus + 1 soj, and probably need flickering flame on merc to compensate your list fire resist.
There's some tradeoffs for QoL features here, going all-in on damage. To list a few permutations:
2x phoenix with viper/2x opal/ff = 16136 fb / 3934 hydra with -91% pierce, with 2x 30 redemption aura, cleansing aura, 42 sorb + 90f/80l res
2x phoenix with ormus/soj+opal/magus = 18609 fb / 4120 hydra with -86% pierce, with 2x 30 redemption aura, 42 sorb + 85f/80l res (no cleansing) <--- recommended imo
30/30 sword + phoenix with viper/2x opal/ff = 17281 fb / 4213 hydra with -93% pierce, with 1x 15 redemption aura, cleansing aura, 21 sorb + 90f/80l res
30/30 sword + phoenix with ormus/soj+opal/magus = 19869 fb / 4399 hydra with -88% pierce, with 1x 15 redemption aura, 21 sorb + 85f/80l (no cleansing) <--- or this one good too
50/50 facets + viper/2x opal/ff = 18044 fb / 4399 hydra with -85% pierce, cleansing aura and 80f/75l res (no redemption or sorb)
50/50 facets + ormus/soj+opal/magus = 20709 fb / 4585 hydra with -80% pierce, 75f/75l res (no redemption or cleansing aura, no sorb, no max res)
The 30/30 sword and ormus setup gives the most damage while still keeping high pierce and 1x redemption aura and some resists/orb, the 20/20 facet shield is impractical because the 4% more damage not whatsoever worth the lost -8% pierce and other benefits.
But you only lose about -6% overall damage and -2% pierce to go up to 2x phoenix and have that double redemption aura / double sorb. But using flickering flame/viper means losing a big chunk of damage, you're down -19% from the 30/30+ormus setup, or -13% from the 2x phoenix+ormus setup.
I will say from experience having a fire sunder build that needs the +fire resist from merc flickering flame puts you in jeopardy against fire damage heralds. One of my only deaths on warlock was to a pack of flame mages in abaddon when they killed my merc, which removes resist fire aura, then chunked me for 4000 hp instantly because I was at negative fire resist. The ormus build can still hit max fire/light/poison resists (probably not at same time as cold, but it doesn't matter) but you do take more poison dps with no PLR/cleansing and have a risk to fire if merc dies
Do you know if you can put 6x Defender Fire in a 6os Crystal sword ? Prolly better then 30/-30 with facets?