To everyone talking about Tai's promiscuity as a problem, remember that Tai has always expressed interest in a monogamous relationship, but hasn't found one and has gotten caught up in the poly scene at her school.
She started out here
http://questionablecontent.net/view.php?comic=728 wanting to be exclusive with Bailey, and after Bailey rejected her, she got into a three-way while drunk and disappointed:
http://questionablecontent.net/view.php?comic=765Later she expresses her dissatisfaction and her desire to "settle down with one person" in
http://questionablecontent.net/view.php?comic=1595 and
http://questionablecontent.net/view.php?comic=1596 It doesn't seem fair to say that just because Tai has had casual sex and threesomes, she wouldn't be a good partner in a long-term monogamous relationship. Why couldn't she be capable of both? (EDIT: Also, it just occurred to me that I don't know if we can be sure Tai has actually had all that much casual or group sex. Ashley and Serena were her first threesome, and has she ever described any other hookups?)
I think part of Tai's problem with finding the sort of relationship she wants lies in her approach--getting drunk and taking off her pants, rushing into hookups, etc. This M.O. is more likely to attract party girls and casual partners. (Note: I'm not saying that all non-monogamous folks are party girls and casual partners, but I think most of Tai's partners have been).
Here, Tai tries a different approach. She doesn't move in for a makeout. She expresses her feelings in a way that's caring, romantic, and not overtly sexual. She demonstrates that she cares about Dora as more than just a potential hookup, and she shows Dora some of what she has to offer as a more-than-just-sexual partner--kindness, sensitivity, and support.
I don't see Tai's pep talk as discouraging Dora from going to therapy. Tai isn't telling Dora "you're perfect, stop trying to improve." She's telling Dora to stop beating up on herself.
One of Dora's issues is insecurity. She feels inadequate and inferior. Remember how she obsessed about the idea that Marten only went out with her as a second-best because he couldn't have Faye? Dora's self esteem could use a boost. Sitting around saying "I'm such a horrible mess because I have these issues" doesn't help you work on those issues, it gets in the way. If Dora learns to say, "I have some shit to work out, but I'm a strong and capable and awesome person," that will give her more confidence to face her issues and deal with them.
Tai is showing a new level of maturity here, and I think she totally rocked in how she handled this.