I agree, that Phoebe seems more likeable than Tam, but I don't really like her that much. To me, it seems like she's going to be a needy character. But I guess you're right, we haven't seen much of her yet. But at the moment, I can't see her doing any other storylines apart from her and Kyle's romance, and being involved with the Braxton clan.
And plus, I think that Tamara can be likeable, it just depends on where she is, who she interacting with, and what she is doing. Like her setting up the music festival was great, in my opinion. But her juggling between two brothers? Not so much.