Story mode should be ok with henchmen since not all that many people run them now.
Other than that i do not think this is a good idea at all.
You said that it should be like in GW1 and be able to do dungeons with henchmen/ Heroes.
Do you realize how hard it was with henchmen?
Even with Heroes it was no cakewalk and you needed to micro them all and carefully choose your skill builds. Maybe things got easier once they let you take on a full party of Heroes but still…it is not easy.
A henchman/hero will never dodge as good as a player and never be able to assert the situation in a game that relies on instincts and timing.
Dungeons are made to be hard and for groups.
If you do not have the 30-40 minutes it takes to finish one path then go do one of the other awesome things in game.