Do resistances and -% debuff duration work in PvE?

Hi, new player. I'm planning my build and getting very conflicting messages.

My guildmate says that separate resistances (stun/silence etc) as well as -% debuff duration don't work in PvE at all. But another person said to me that they totally work in PvE and that -% debuff duration is preferrable to separate resistances.

It's kinda a huge deal since I'm planning my traits. So which is it?
I'm never ever ever doing PvP so I'm only planning for PvE.