Hey OP, I just wanted to say that the same happened to me while farming DT. It didn't feel as bad and I think I know why. It's because I could use my DT before him being 7*. Every star made him even better, sure, but I have been using him ever since he was 4* for smaller stuff and slowly built to be the beast he is at 7*. Also, DT wasn't as terrible a grind because he's only one toon, who doesn't need a partner; and lastly because you can get a bunch more shards for him in other places, such as the Empire Assault Battle.
Vets on the other hand are useless out of JTR's Hero's Journey. I've tried using them for minor stuff such as GWs (back before I could sim it) and they simply weren't good enough. So yeah, it's the fact that not only are you farming two toons from the 16-energy nodes, but also that they're useless until JTR comes back, and they'll be useless after we get her, and we all know it