I entered the quest on elite. Set the hireling to attack, hit the stopwatch when the knight transformed into the wolf, and stood back and healed the hire until it killed the knight. Then I reset the quest and refrained from healing the hire while the knight killed it. I estimate my margin for error is probably around +/-:02.
SADIELE (L20 fighter/L2 LD):
Average time to kill wolf knight: 1:35. (fastest time was 1:23, slowest was 2:14).
Average time to get killed by wolf knight: 1:53 if allowed to drink pots. (I ran it once where I put her on passive and she only lasted 1:17)
PANTHER (L20 fighter):
Average time to kill wolf knight: approximately 6:32 (I quit after 3:16 when the wolf knight was still at 50% health).
Average time to get killed by wolf knight: :57 (quickest fight was :53, longest fight was :59)
eOWLBEAR (L25 whatever):
Time to kill wolf knight: 4:31 (I only ran this once. It could be a crazy outlier, but I doubt it would ever get close to 2:00)
Average time to get killed by wolf knight: :37 (quickest fight was :35, longest was :39)
For the heck of it I ran Rovegar through Murder by Night once to see how long it could take him to kill the knight. I got interrupted before I could run one where he was killed by the knight.
ROVEGAR (L20 fighter/L1 LD):
Time to kill wolf knight: 3:23
The Owlbear is by far the least able to take damage despite having 300 more HPs than Sadiele. It is a serious mana sponge in one-on-one fights like this. I went through almost 20 heal scrolls keeping it alive, plus 500 SPs of CLW, 1 lay on hands, and healing spring. The other hires only needed healing spring and CLW to stay alive while fighting the wolf knight.
Based on this information, plus what I saw in eGH, I find it hard to believe the eOwlbear has 200PRR. I suppose it is possible that it has a really high PRR and the AC is incredibly low so even though it has high DR, it gets hit a lot more than the fighter hires. Regardless, it really should survive longer than the panther does in a fight like this.