Simple question, hopefully with a simple answer 
DOP in Cubase 9.5 was an unusable abomination, that forced me to stick to Cubase 9.
Have they fixed it yet? Can I do a time-changing process to a long piece of audio, then edit it into pieces, then make changes to those pieces without ended up with GB of edit files and totally broken audio content?
It’s definitely improved in C10 – essentially bringing it up to Nuendo’s version of DOP from what I can tell. But I can’t be sure it works really well yet, I haven’t tested it thoroughly yet. So I know that’s not much help, lol. But I am totally with you about how frustrating DOP was before, especially when it was launched. I was a very strong critic of its shortcomings and Steinberg’s lack of proper testing before it was launched. While they did thankfully make progress through the 9.5 lifespan with many bugfixes, I was never 100% comfortable with it for any complex workflow. For simple workflows it eventually became pretty solid.
Personally, I found with DOP that its effectiveness/usability/stability was very much subject to specific workflows and sets of plugins… so while I can say it has definitely been improved, I’d suggest testing it out yourself in your specific scenario. It’s getting better, but it may not be up to speed for your workflow and plugins yet. Personally, I still wouldn’t trust it for anything elaborate yet. For what you described, I’d be skeptical that it would work as we would both hope, but again, I haven’t tested that scenario yet.
Overall, I think the C10 release is excellent. It shows a real willingness on Steinberg’s part to listen to their customers and for me, is a very good step in the right direction. Remains to be seen if they keep the positive momentum, but I’d say C10 is the best Cubase launch in years. As for DOP, yes, another step forward, but I would keep my expectations/hopes in check.
Hope that helps a little.