Increased damage taken

I have really peculiar problem.
Whenever my char is over low life it takes damage that takes it below low life level (while mapping, didtn notice this before maps), and RF burns more until HP reaches around 35% or less, then damage gets normal.
For example white skeleton in t1 map does 3k on first hit, then around 100 for rest (true for other mobs as well)

Char is WoodRiser (planned for totems put changed my mind), I am really lost of what could cause this, and really annoyed by that, its not really playable.

Only thing I can think of is maybe your Fire Resist isn't capped, until you hit low life and then the 25% Fire Resistance while on Low Life from Rise of the Phoenix kicks in and caps you out, thus reducing the damage you take from RF by a TON.

Okay didnt notice lack of ~10% fire res, but whats with those mobs though!
Thanks for help

Edit:
Added res, and fixed my problem, also didnt notice any extreme hits from mobs anymore.

Though something is wrong. RotP low life bonus either persist after poting out of low life, or im losing some resist other way.
Also dmg taken from hits while RF is active in that state (Not low life, but with bonus from low life) is highly increased
Pot that adds hp instanly (panicked in my test) do not retain bonus, only with over time pot does it happen. (Degen eats through life pot, then reaching low life it gets bonus and pot kicks in and retains resist bonus)
Problem with resists is sure, hard to test damage from mobs though. I do believe its also something wrong however.

I only skimmed, but it sounds like you're describing a very old bug that is quite well known in the Bug Reports Forum.

As you can see in the second link it is a display synchronization bug. Your client is lying to you, sadly :p

The easiest solution is to cap your fire resists so that the bug doesn't happen.

Oooh that explains everything even "very high dmg" since hits just resynch my hp to 35%. I switched to predictive yesterday to see how it works since there has been some lag spikes on my end.
And 2014, this must be quite a bug if it still persist.

Also I might have searched before posting, sorry for that, but thanks for explaining this to me.