Firstly, 47 necro is completely viable.
Secondly, you almost certainly got your tactics wrong. Since you had an army you'd probably have done better using weaken and wither, then poison and scourge.
Thirdly, while you did parry one attack, you are slowed. Another mistake.
You could alternatively have gone for a blind then rescue.
Fundamently though you died because even though you knew you had additional enemies on, your didn't check for their approach when it is easy to run from the entrance to where you were.
And I'm pretty sure based on the feedback everyone else seems to give these characters, that they full looted you because of some behaviour of yours.
Finally, imm exp is a lucky bonus, not a right. Did I get imm exp for taking on Pacman's wrecking ball of a warrior as Chamst even when I knew he was very likely to destroy me? No I didn't. We should never be certain that something will give imm exp because then people will game it.