I was fooling around with simcraft and chardev today myself. Particularly I was curious about the 397 gear level for those who did heroic Firelands and, like me, have yet to get their hands on a legendary.
I came up with these two profiles:
397 gear level w/ heroic rag (41303 dps): http://chardev.org/?profile=294565
397 gear level w/o heroic rag (41046 dps): http://chardev.org/?profile=294586
397 gear level w/ 4pc T13 (40885 dps): http://chardev.org/?profile=294557
I found it particularly interesting that both of these profiles came out with higher dps than using 4pc T13.
In the second profile, my initial assumption was that placing all red epic gems in the chest would be better, however it left me stuck 4 points under cap. I tried matching sockets. Turned out to be slightly higher dps and at hit cap.
Keep in mind these profiles also use 100% epic gems and assume you have DI.