It is possible your RAID volume is not getting the TRIM command and therefore, not being optimized. First, try to optimize the drives with the Intel® SSD Toolbox; however, this depends on the SATA controller and driver being used. Another option will be to optimize each drive separately and mounted as a secondary drive.
this controller doesn't seem to support trim under raid0. nice idea about mounting as secondary drive..i'll have to back everything up and see if windows exploded after! lol