The whelps also reduce the damage from the Behemoth's fire breath if I'm not wrong. Also, your tank might off survive the roar without the whelps on him :P Stun + adds = lots of damage even if those adds usually don't do any worrysome amount of damage.
We did this on 10m during the last reset and had the Time Warden with the Storm Rider up (we didn't release the 3rd drake so I'm not sure on that one. But it weren't the whelps so I guess it was the Nether Scion) - Since all of the videos and guides from Beta seemed to have more or less the same drakes active it took us a long while to adapt our strategy and see for ourselves what's actually happening when and why.
Either way, keep up the good work, love it.