I think there's two arguments here.
Argument one, skill vs RnG: People who have invested their effort into learning the ins and outs of all the kinks of nwn pvp don't want to lose to a bad roll.
My opinion: I think RnG is the great equalizer and will actually make pvp fun for a wider swath of players, and I am definitely in the camp of make wizards scary.
Argument two, do we need to reinvent the wheel to make save spells a thing?: People are worried that a drastic overhaul of the spell system will move us even further away from the game we have been playing for over 20 years in many cases.
My opinion: Probably not. I don't think the change will be as drastic as people are making it out to be, but it seems like a lot of work to just end up in the same space. Or worse, going too far and then having to roll back when 75% of the server are now dc casters. I think you can accomplish the same thing by just boosting the current dcs and adjusting as necessary. That turns a months long project (or longer) into something that can be accomplished in a couple of days. I would personally look to boost specialists and leave generalists as they are, adding pvp caliber spells to the schools that are lacking. And any boosts to dc gotten from a specialists school (I would start with +3) doesn't stack with shadowmage, it takes the higher of the two. Simple, clean, and if it needs to be adjusted no one is really getting screwed over.