It's been stated by the devs that there will be more good companions introduced as time goes on, they just wanted to get the evil companions and to have people try the evil options so that those options (which they know to be less common) can get an adequate amount of testing early on. I think the game actualld does make it interesting to play as good.
If you kill the goblin leaders in the whole grove questline, you get to enjoy a party with the tieflings you saved. It was the sort of thing I can't recall experiencing in a game like this before and it really made you feel rewarded by letting you interact with the people you saved and really absorb the fact you did a good thing for these people.
