Damage of enemy Skeleton Mages is too high

Not a technical issue, but it seems that the damage of those skeletons is overtuned right now.
This season I decided to try a very tanky build: 90% phys reduction, blocking, spell suppression maxed, resistances at least 79%. I'm not far into the endgame (t5) maps and here is my current problem: skeleton mages - white ones, not magic or rare (especially the fire skeletons) are melting my total life with ease and I have no idea why. I never had any problems with them and now even with slayer overleech they are killing me.
I posted this in the subreddit and had a couple of replies that other players are also experiencing this which is why I'm posting it here again. Even a RF player with 84% Fire Res is getting killed by those Skeletons.

I just died on a tier 3 map. One white firemage sekeleton got me oneshotted with a fireball. I lost like 90% of my life from the hit and the ignite klilled me pretty fast. My 2 Lifeflask, vitality aura and my Stonegolem wasnt able to heal against it. Afterwards I searched for a Map with those enemies and it looked like this:

Blue Champion Firemages:
https://clips.twitch.tv/SmellyShortNeanderthalM4xHeh-3JrP0elNn5wm0YgH

White normal Firemages:
https://clips.twitch.tv/InnocentSpunkyTomatoRlyTho-bhDwTTtQkaJqHnOU
My Zombie had 18909 HP

https://clips.twitch.tv/EasyPerfectMarjoramMVGame-ZhCpcodB4oA_8BDe

Ive recorded some more clips.

Overall it seems that the Champion mages deal less damage compared to the white ones.

Just a little bumb: there are now more replies in the subreddit-post to this issue: https://www.reddit.com/r/pathofexile/comments/smtlhp/enemy_skeleton_mages_and_their_damage_hc/