I personally dont think your going to gain much, if any, performance by splitting the OS and the applications to different drives. Most apps. rely on many Registry entries, and if these end up pointing to files on other drives, or partitions, it makes it more difficult to maintain backups without those entries going ‘out of sync'.
In fact the only benefit is the initial loading times.
Use the SSD for the OS and apps. and RAID the other two if you need too.