Primordial Block Map (t15) - instance crash reentering arena (and other weirdness)

After dying once to the boss (strange amount on damage, see below), tried to reenter the arena but had an instance crash.
After that, the login/character screens were plain black, with just the GUI being shown (still functioning) , the background models/animations were enterely missing.

About the boss: is a bit strange that it could one-shot with the charged (lightning+phys ?) attack a Juggernaught with 9.170 life , with 7 endurance charges and IC active during the fight, was also a "blue" map with no damage mods active...
Never had similar problems with other bosses...
Is it intended to do such HIGH damage ? seems a bit off ;)

Thanks, and keep up the good work ;)