I'm sure there's going to be people who get pissy if you can't spend 4+ hours on an exp group, but that's their problem, not yours. just be upfront and say "yo, I've got about an hour or two" when you join a group, and it would never hurt to try and find a replacement shortly before you have to leave.
I'm new and have very casual playtimes myself, so if you ever want to chill and duo with a necro just shoot me a tell.
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