I never used the outfit I just killed everyone.
The Henchmen do have quests of their own, but nothing to really help the story any further. And they cost you XP. You should be able to finish the game without a henchman, but maybe you like it more with one, whatever you prefer.

That Hoff guy isn`t really important, he`s part of a quest you can pick up in the Moonstone Mask from one of the courtesans.

The outfit is used to enter the tavern, if you don`t have it you have to pay to enter i believe.

As Arathorn says, you don`t really need henchmen, unless you feel you could use some help, or play a class that could use some melee power for example. But they`re not plot-related. If you decide not to use a henchman, it`s still interesting to hire them and talk to them a couple of times to see what quest is related to them (you best do this when you gained several levels, because they don`t talk all the way untill you reach a certain level). They all need a certain item in each chapter and if you find it they give you an item in return that boost your own stats. And these items get stronger each chapter (like an amulet that gives +4 strenght, 12 spell resistance and immunity to fear in the end). Not bad i would say.