I only see bonuses on DLC armor as a problem for console players who can't mod their game. If the set had some bonus I really want, it is very easy to just add that bonus to an existing armor. I can live without the special visuals that new armor would have. And if I really wanted the visuals, then I could choose to buy it.
If they did add something like a new workstation as a DLC, then I would be upset unless it was part of a full expansion. But I didn't think they would go that route. It would alienate a lot of fans.