I came across this , do you guys know about this ? I just kinda found out.
No wonder I have some difficulties doing certain bosses.



Boss elemental resistances vary a lot
Information

Just something I noticed digging around poe2db. Unlike in poe 1 where bosses had 40% elemental and 25% chaos resist across the board, with pinnacle bosses bumping up to 50%/30%, in poe 2 it seems like each boss has its own unique set of resistances.

Count Geonor only has 30% cold resist, 0% everything else.

Jamanra has 30% fire and lightning resist, but actually negative 30% cold.

Doryani has 30% fire and lightning.

I'll use fire%/cold%/lightning%/chaos% for the rest:

Sekhema trial bosses

Rattlecage 75%/-50%/30%/0%

Hadi 75%/-30%/0%/0%

Rafiq -30%/75%/0%/0%

Ashar 30%/-30%/30%/0%

Zarokh 30%/30%/30%/0%

Chaos trial bosses:

Uxmal 30%/30%/30%/0%

Chetza -30%/30%/0%/0%

Bahlak -30%/0%/75%/0%

Trialmaster 75%/75%/75%/0%

Random other bosses:

Candlemass / Meltwax 30%/30%/0%/0%

Rathbreaker / Caedron 0%/0%/0%/0%

Mektul / Gulzal 75%/-30%/0%/0%

Tor Gul / Zar Wali 75%/0%/0%/0%

Omniphobia 0%/0%/0%/0%

Olroth 0%/75%/0%/0%

The King in the Mists 0%/0%/0%/50%

Arbiter of Ash 75%/75%/75%/0%

Xesht 75%/75%/75%/0%

So if you're struggling against a specific boss it looks like it will be a good idea to plan your elemental kit ahead. One no-brainer thing to do is avoid using fire damage when you do your first sekhema trial because the boss has 75% fire resistance, and probably use cold instead for that sweet -50%.

It also seems like everything has 0% chaos resistance except king in the mists, while some pinnacles have 75% in every elemental resist.

As for physical damage, at a quick glance it seems like every boss has consistent armor scaling starting at around 2800 at level 65, going up to 6800 at 80 and further beyond that.