I tried it yesterday in Tally and your assessment is the same as mine other than the pulled pork which I found to be quite good.
I got the two meat combo with brisket and sausage and my wife got the pulled pork sammy and then we split them in half.
The first thing I would say is that all of their seven sauces are EXCELLENT!!! My main problem with both Piggies and 4 Rivers was that while their meat was better than Sonny's, their sauces were not. Mission on the other hand had great sauces and even the "worst" of the 7 imo, the Tupelo Honey Heat was still decently high quality. Even their "Bay BQ" sauce with Old Bay seasoning in it which is supposed to reflect Maryland was surprisingly good. But their Texas Style and KC Style were great, some of the best chain sauces I've had. My ONLY complaint sauce wise (and it's tiny) is I wish they had a South Carolina yellow mustard style and a Florida Fatboys/Sonny's mustardy red sauce to compliment all of their delicious red sauces.
As far as the meat itself, the brisket was one notch below Piggies and 4 Rivers when they were at their best but better than the worst versions I've had from Piggies and 4 Rivers. Since I've been to Mission only once now, I'm not sure if they will consistently have slightly worse brisket or if that's a one time thing. However, their pulled pork was on point for a NC style and it worked great with both their Vinegar "sauce" and all of their red sauces. It wasn't the best pulled pork I've ever had as I frequent Red Bridges in Shelby NC, Bill Ellis in Wilson NC and Pierces Pitt in Williamsburg VA at least once a year or so, but it's the best I've had in Tally by miles. The sausage was great as well.
The sides were decent too. The baked beans obviously use their Texas Twang which has an A-1 style tanginess to it so they were pretty decent. I probably prefer Sonny's beans though. Their mac and cheese was better than Sonnys and their fries (which were given to us as a freebie) had a good seasoning on them and were crispy.
Dare I say...Tallahassee may not be a BBQ wasteland anymore? I don't know, one trip isn't enough to say definitively but it is a very promising start. I would say that a Moes chain would still be worthwhile as an addition.