Posi 1/2, Yin, Manticore, and Numina aren't that bad and are all 10-40 minutes on a quick team, but I mostly agree with you. There are better ways to get merits and I don't think I've gotten TF commander on a single character since I found out about the mayhem mission contact redside. Why would I sit through 6 task forces when I could do Invader in less than ten minutes?
If those repetitive missions gave good rewards versus time spent you bet people would be running them more often.