Kruin and Inquisitors, questions Options

[Kerkes]

well, I must say I'm a bit surprised nobody asks help about this one.. (in my latest run, it was the hardest battle for sure. 17 reloads! AAAAAArrrrggh!)
The thing I wanted to ask is this:
Is Kruin immune to "dispel magic" cast from an Inquisitor?
I once played the game with a custom Inq in party (was lvl 18 by the time I met Kruin, I did some of WK, Umar Witch etc.before going back to Alkathla from Underdark). As soon as his buffs kick in, Inq fires his dispel. I get a message : spell ineffective?!
Now, I quit inquisitors for good, and took a blade instead, which, I must say, are 10 times more useful than an Inquisitor will ever be (if you want a powerful dispeller, that is) regardless of his Avenger sword.
Same battle, blade is lvl 23.
Took 4 reloads, and it worked ("remove magic" was succesful.)
What's up with that?