I think you're overestimating the number of people getting DM with "cheap TPAC flights" and an Amex -- even with the MQD waiver you need about 8-10 "cheap" TPACs to make MQMs. As others have pointed out, travel at peak times is terrible for everyone.

I'd agree that generally the benefits aren't worth it, except given your typical route of SLC and BOS (two cities that get hit with winter weather) as soon as you get trapped by WX you'll appreciate the priority handling you get as an elite. During one winter storm when the general public was waiting 17 hours for callbacks, I got through in 7 minutes and got the last remaining seat on the flight I wanted.