Sadly, the D hasn't looked as good as we had hoped. But I wouldn't abandon ship just yet. It takes time to work a new guy into a starting lineup. It took time to work LMA in, and Pau. No reason why Dedmon should be instant. We all know that Dedmon can play D, just like we all know that he is limited offensively. Pau actually looks to have benefitted from coming off the bench, IMO.
As for not matching the other team's intensity coming out of the gates? Everybody's gunning for the Spurs, for obvious reasons. They come out with their max effort, and eventually punch themselves out.
Pop always says that "good defense leads to good offense". But the second half of that should be that "bad offense is the same as the other team playing good defense - and it leads to them getting easy looks on the other end." The Spurs' offense has really struggled recently. Some of it is Dedmon, but basically all the starters except Kawhi have struggled. That has led to a lot of gimme points for their opponents. At least that's the way I've seen it. The Spurs have shot themselves in the foot a LOT. I think if the offense gets cleaned up, we'll see a lot less easy points for their opponents on the other end. If nothing else, more makes for the Spurs = fewer opportunities for opponents. And makes force them to inbound the ball, which gives the Spurs' defense more time to get set up.