It was more that Long was an unknown quantity at this level, at least for me. He didn't even play in the MLS until this season at age 24, so doubts were warranted at the time, I think. He's definitely done very well, surpassing most people's expectations (probably yours and Marsch's as well!).
DP should not be an everyday starter, and he isn't it. Two injuries to guys in front of him (Baah, Collin) are the only reason he is starting. He's okay for a backup, but that's it. With Baah out for the season, we need a CB better than DP as competition for Collin and Long. Hopefully one is coming in the summer.
Doubts were warranted, but if you watched him closely and paid attention to him with RB2, he had everything. THe speed, athleticism, and his ability to read was good enough. He was MLS quality for sure, the only question was how good he'd be. I liked him, but didn't even think he'd be this good.
And in regards to your post Iced, I actually think Muyl has been passing the ball a bit better than he did last year. Considering he had a broken face through much of training camp, I actually like where Muyl is at.. He's only started 7 games too. The bigger problem by far is Sacha who has zero freaking goals. And Royer has to be better around the goal as well.