Yep, that's what Crit Resistance does - this even applies when the necrotic buff is on enemies, so you can dodge a crit even if a crit is supposed to be a 100% chance.
Poison Resistance lowers the damage of the poison damage over time effect. It starts at 50% of your maximum HP (100% for potent poison), and is lowered by the resist stat.
I'll clarify both of these in the info section.