Mixed workload testing is standard practice in the enterprise space, but it's just now becoming more popular for desktop storage benchmarking. In order to make this testing viable for client workloads, the number of data reads increases to 80%, leaving 20% for writes. AHCI, the underlying protocol for SATA, is a half-duplex interface, so devices can only read or write at one time, never both. This increases latency as tasks end up waiting on each other.
The JMF670H performs well in both sequential and random mixed workloads. The same rules still apply: low queue depths weigh heavier than high queue depths for desktop use. The baseline starts at QD2 though, and ramps to QD4 for multitasking.