If you have insurance the 2nd T will likely charge at least what your insurance would reimburse them if they were to file. Sliding scale is usually for someone without insurance. So it may cause financial strain.

I have had 2 Ts at the same time twice in my course of therapies. One of them has been consistent throughout and I still see her now. One time this worked extremely well for me. The Ts were collaborative and tackled different issues. On another instance it got extremely sticky and hurtful for all of us because the Ts stepped on one another, creating discord and a lot of tension.

DBT if done as it should be - should be fairly supportive if they have all the components. DBT skills group once a week, therapy at least once a week, in between coaching calls, etc. The group would give you another "appointment" a week, and a group skills therapist.