Ok, so I took the first advice and asked for a soulstone. Died at around 60%, used SS, and went all out. Kicked some serious ass there with all that rage. I ended up 2nd, slightly behind our best rogue. (The rogue and I did 21% of total raid dps, almost equally shared, woot

)
Highly recommended.
As for the intevene thing, tough to time it really. First, you have to make sure there is enough time for the next pounding, so that you can recover from the hit. Then it is not certain that you will be getting it. And it is not some huge reduction, 20 k or something.
As for tanks interveneing each other, I think same OT should be on this duty right? Otherwise, there could be threat gap between the MT and the OT's, and if an intervene does not take the knockback, dps will pull agro.