My plan was to start a new run with the new class, and not skip main campaign, as I hadnt played in long time.
I expected I would have some npc early that allowed me to go to VoH area, before I finished main campaign, so I could just go there, unlock mercs, and go back to the main campaign, making use of them to spice up gameplay.
But as it is now, I only could either skip main campaign, and go to VoH, or as it seems, I will have to finish main campaign before getting the option of going to the new VoH zone and unlock mercs.