Did you do the firmware update and create the fusion BEFORE cloning? After that, clone it. After cloning, you'll likely have to reinstall yosemite. Not a clean install, but just a recovery install. And make sure your do a disk repair and permissions repair too. After doing all those, mine is working amazingly as a fusion drive.
----------
Hey. I did use blackmagic but it's not giving realistic results. It's showing like 20x slower than the HDD but I can attest that this drive is probably 4-5x faster than the HDD, based on my experience with it so far. I think I have to let the OS get used to the drive and "learn my habits" before I run the tests. I'll try in a couple of weeks.