I posted this over on the US forums, but I wanted to see what anyone else in the beta thought about this, or if I'm just being crazy:
Because the live rotation for assassination is pretty fluid, and we've received essentially no mechanics changes, the fundamentals of the rotation in MoP Beta is pretty fluid as well.
However, Dispatch procs can be frustrating at times: If you're pooling up for Mutilate and get lucky with a Venomous Wounds proc right at the end, you're granted a little breathing room; the 10 energy from that plus the regen during the gcd is essentially right on the cost of dispatch and you can flow smoothly into using that proc and moving back into pooling for your next move.
When you don't get the VW proc, or get it earlier when you're pooling for Mutilate (say at 30 energy, so it's still too early for another tick of Rupture when you use Mutilate), you wind up with a Dispatch proc at 0 energy. This interrupts the flow of the rotation, it feels like riding a bicycle and wanting to step on the pedal hard to get some speed, and having your bike chain fall off at that moment.
It seems like there would be some possible options to alleviate this, either make VW proc 100% of the time, or make Dispatch procs free. I like the latter better, imagine how the fury warrior rotation would feel if Bloodsurge made Slam instant, but cost rage. It just wouldn't feel right.
tl;dr: Dispatch procs off of Mutilate should be free, it makes the rotation more fluid.
PS: Another thing that would be fun is if you brought back Overkill and Cold Blood. Turn Cold Blood into a real dps CD by tying the Overkill regen solely into Cold Blood activation. The ability would become something like this: Cold Blood: 2 min CD, When activated, you regenerate 30% additional energy for 20 seconds and increases the critical strike chance of your next non-periodic offensive ability by 100%.