dps value of feral set bonuses?

So I've seen it said that the T12 2pc bonus (Fiery Claws: 10% bonus to Shred/Mangle) translates to about 5% dps increase. Has anyone calculated what the dps value of the T13 4pc bonus is (free Ravage every time you pop TF). It should translate to about 7-10 free ravages over the course of the fight.
600-800 DPS: T12 2PC, T12 4PC, T13 4PC

1600-1800 DPS: T13 2PC

600-800 DPS: T12 2PC, T12 4PC, T13 4PC

1600-1800 DPS: T13 2PC

Sooooo..... you're saying that both T12 bonuses and the T13 4pc are all about equal in value? I ask because someone I know was considering dropping the last of their 378 T12 items and the 2pc Fiery Claws bonus for LFR T13 items in order to get the T13 four-piece. I thought that Fiery Claws was better than that...
No Bonus: 37780.94
Tier 12 2Pc: 39010.93
Tier 12 2Pc: 38656.47
Tier 13 2Pc: 38565.20
Tier 13 4Pc: 39647.79

That's my gear, didn't change anything except for the set-bonuses, only 1 set bonus active at a time. What also must be taken into account is that if you are using T12 bonuses, you have to account for the loss in Agility and Secondary Stats.