HC is too hurts, is it normal?

Did Warmane server adjust anything because it's a private server?

What the hell do you even mean? What HC, what hurts, which realm?

I mean Hard core instance in PVE frostmourne server.

if you mean wotlk-raids then yes.
Frostmourne uses the "lordaeron" core when it is about raid difficulty (as far as I know)

and lordaeron is an hardcore realm where Raids have been buffed (boss have more hp and shorter enrage timers, maybe deal even more dmg but I am not sure)