I had hoped that .5.10 would cure this, but I am still getting massive CPU overloads when inserting, moving, turning on or off, or deleting plugins. The real-time meter goes to max [avg. load], and Cubase hangs for 3-30 seconds. This does NOT happen in 9.5.40, with the exact same projects. Something has obviously changed between the two versions (I skipped 10.0), and not for the better. If I increase the asio buffer a lot (1024+) the problem is less severe, but it really shouldn’t be neccessary.
Edit/update: it seems to not be actual CPU overs, the system monitor shows no spikes on any cores, physical or virtual. This is simply Cubase choking on very simple plugin changes.
Edit/update2: After having struggled with this for weeks, I finally caved and went back to 9.5.40. Despite the less colourful interface and missing features, the creativity is now back on track. I’m eagerly awaiting a usable 10.5.x.