I was seeing a 3 set of Treants with RoR and one stack of blades doing just over 400k rake damage (or about 25k a tick). This is an addition to their melee attacks which was coming out to about half of that.
Uhh... were you not in cat form? You have to be in Cat Form or they inherit your pitiful caster form AP.
Edit: Here's a log if anyone's interested. ~7 minutes of combat with flask/food as HotW/FoN (Treants are pets so they don't show up in my damage, you have to click the arrow next to my name on the log I linked):
http://www.worldoflogs.com/reports/r...um/damageDone/
Treants were 7.73% of my damage and Rake ticked a total of 144 times for an average of 33,170 damage per tick. During Rune I dumped my charges (waiting for procs inside the Rune when feasible) and outside of Rune procs I banked charges, waiting until I was about to hit 3 before spending one.
I'm not raid buffed in this log (which means I'm missing mastery).