Far as I remember, hold person was very likely a double-roll spell — fort+fort or fort+will probably.
Paralysis was reworked to exclude full-body paralysis (which sucks a lot

), but hold seems to be the same.
Saves system feels quite different compared to 20 years ago.
Under the old system saves in the 70s (very hard, if possible, to attain with state-of-the-art gear of the time) would make you close to immune to monster bullsh*t,
now I get routinely blinded/plagued/whatever in just a few attempts.
My guess would be the saves chance after all the number crunching has a lower max cap.
It also got deadlier with the hour-to-minute affect timer transition.
Just like dirt kick turned from a fringe skill to something quite reliable.
You don't know the current moon, his spell power and feats. If you think it's a bug - post in right section.
The most effective set he could take (and therefore my guess) is: penetration, penetration, combat casting.
Thanks to the team effort he likely has full books, so Raistlin's spell enhancer (+1-3).
Staff of Magius (+3)
I would bet on ~43 cumulative spellpower at the moment of the battle, given a good but not perfect moon.
Penetration would probably add *handwaves* another 3.
With old system saving a double-check of a 46-level mob VS 80 saves would be peanuts.
Not a bug, in the same way lash failing against flying enemies is not a bug.
It was designed like that, plus a bit of luck
