Search:

I think Cellar in Thunder river can be 2-maned, the rest is stricly solo experience (only one person can enter)

Paikang is a zone, last zone of ROGS expansions and mobs are +85 lvl (and they hit HARD).

Whole ROGS expansion provides a challenge for solo player for sure, much harder than vanilla aoc.

AOC...

There is no duo group content per se, but Khitai zones (especially Paikang) and Dragon Spine zone can be still a challenge even with two man groups (those are brutal for solo play).

Any class...