Killing machine is a very valuable talent for frost tanks and for frost dps. you have to look at it from both a total throughput perspective and a utility perspective. a 100% aoe crit on
your crit chance went up 10% from that talent. If you're a tank, however, and you only have 10% crit chance, you will only normally expect 1 of those 10 to crit. Killing Machine then has a high chance of using all of the procs. We'll say that 10% crit chance comes up enough to wipe one, you still now get 5 procs, and suddenly your crit chance on those abilities went up an average total of 40%.