Double Mangle (Feral Druids)

You need 2 feral druids, one of them has to put mangle on the mob and also rip like any normal dps rotation, then the other feral druid (bear or cat) has to mangle before the first bleeding of rip happens, that is within 2 seconds after the first druid used rip.
You will see 2 mangle debbufs doing 60% of extra damage to bleeds and shred. Also remember the one that needs to use rip is the one that put the first mangle.