Bug 2.572.952.582 Agonyguard from unique chest doesn't loose Energyshield

Hi,

i ran in a problem with an unique chest and the spawing agonyguards.
Though i hit the respective instance of the agonygaurd with lightning lance and
physical stabbing, the energy shield of the agonyguard just rarely took a dip.

And though i was constantly hitting the agonyguard, the ES recharged while
hitting the agonyguard. Only periodically the ES would be gone and damage
was possible.

I've been running running around the ssecond incarnation for hte agonyguard for
5 to 10 minutes, and the 3. incarnation is totally unkillable...

Some time ago, i got another unique chest and the agonyguards there were
killable

Bug ID is 2.572.952.582

Cheers,
Markus