My cake "truffles" (no pop) are awfully mushy after they defrost. Delicious, yes but they do not hold up, especially outside. I had been selling them with a drizzle of royal icing on top but in North Carolina humidity that's not cutting it. I'm wondering if I should throw them all back into the mixer and add more cake, then reshape? OR, for the wedding I have coming up, if COATING them in chocolate and letting that harden will completely solve the handling issue? Any advice?

What are you using to bind them and how much?

My homemade buttercream. I add enough to get the "dough" to pull away from the sides.

Hmmm. I'm not exactly sure what the issue would be. When I make mine, I only add a couple of tablespoons of buttercream as a binder, and I don't put them in the freezer to set up anymore. Sometimes that temperature drop from the freezer to room temp could be the problem. I would add a little more cake and reshape them.