I didn't like the fact that volus were going to be added, but it turned out better than expected. As someone else said, they're very fragile and not to be played as frontline fighters, but they have a unique support role in MP gameplay. So basically I'm no longer opposed to having volus in MP right now, but I probably still won't play them all that often either. At the very least I'll refrain from kicking people just because they're using a volus character ^^
That said, I really think adding 4 volus is way too much. It would have been a lot better in my opinion if you had added at least one new salarian character or any other race that doesn't have too many class options yet. As of now there are (if I'm not mistaken) a total of 2 salarians, 3 drell, 3 vorcha and 3 geth. All of these races are a lot more capable of handling ground wars, so I would have liked it more if the volus were limited to 2 characters so we could have some more of the others I just mentioned. Oh well, maybe later if you decide to make more multiplayer DLC...