It’s weird to hear that “A lot of people have issues with h.264 because it can cause lag from high cpu usuage or strange errors”, I though decoding h.264 is like a menial task for any even not so modern CPU, even without a dedicated hardware decoder (which all CPU/GPU/APU combinations, thus all systems, have nowadays). This is the kind of sentence one would have expected to hear 10 years ago, but today?.. And how can this happen to a system that was built for video editing? My only guess would be that there’s a software problem causing this, not hardware.
Anyway, getting back to the original question: Apple ProRes is not the same as uncompressed; it is also compressed, also lossy, and also has to be decoded. Which could cause high CPU usage in some cases. In my opinion, HDD speed should not be a problem in this case, as any normally functioning HDD should be able to easily handle 220 Mbps, unless it has some problems or the system is somehow mis-configured.
People tend to have excessive requirements for storage speed these days, see the GoPro case (recommending micro-SD cards with sustained write speeds of 90 MB/s for a camera that shoots at a maximum bitrate of 60 Mbps).