"90 per cent write and 10 per cent read"
Umm, I watch what is on my DVR so wouldn't that be 50% write and 50%read? A standard drive won't have an issue with a DVR as most encode at around 6Mbps or so so even with 5 streams, that is only 30Mbps, which is not even close to what the drive is capable of.
These drives would also be good for packet capture devices that just capture and write most of the time. Unless the unit is actively used, there is no reading going on and even when it is in use, writing takes priority. Having the user wait a little longer is no big deal compared to trying to buffer multiple 10Gbps links. Run out of buffer and the data is lost, make the user wait and preserve the data.