Yes they can. Showing overcapped resistances for the player was a quality of life feature added a long time ago, would be great if the same were done for pets now but I’m not holding my breath.
Yes, overcap does counteract resist reduction debuffs against them just like it does for the player.
I wouldn’t say it’s as necessary in general for pets as:
-
They typically can end up with magnitudes higher amounts of health than players. It’s not out the question for things like Briarthorns to end up with 70k or more health for instance.
-
Some of them like Blight Fiends are also easily replaceable with the transmuter so you can keep feeding corpses to your enemies.
-
Another niche case are pets like Reap Spirits and Bound Spirits that are largely unkillable allowing builds around them to go ham on offense.
It’s definitely worth overcapping a good chunk of them but some pet experts will tell you based on experience that builds around some of the more tankier pets like Ghol and Blight Fiends can make do without certain ones. The only mastery pets I’d say where overcapping every one by a significant amount is vital is with Raise Skeletons due to their fragility.