Long story short, it checks your CHA against their MR. The more your CHA is above their MR, the lower the probability of a crit resist. Level difference does not make as much difference with crit resist as charisma does.

Thanks. As someone mentioned above though, While level difference may not matter for CRIT resists, it DOES matter for normal resists. Can’t have a crit resist without a normal resist first. Or is the crit resist a totally seperate roll?

It is a separate roll that happens after the resist roll
The lull line of spells has a higher resist rate than other spell lines
In my experience level difference has always been the biggest factor in resist and Crit rates,but this comes from a 255 cha Lvl 60 enchanter, so my bias may be skewed.

I’m no 60 enchanter with maxed CHA. I’m just a poor ass Druid with 90 Charisma trying not to die in the bear pits.