Horn of Winter underrated?

[Quepha 0]

I was doing a bit of reading about Frost Knight dps and the guide recommends Runic Attenuation or Murderous Efficiency for the T2 talent, with Horn of Winter considered to be underperforming the lot, but that doesn't make sense to me:

Horn of Winter generates 2 Runes and 25 Runic Power on a 45 second cooldown.

Murderous Efficiency has a 50% chance to return a rune when Killing Blow is used, but I seem to only get about 2 procs (avg. of 1 rune) per 45 seconds, so Horn of Winter strictly generates more runes for me (in addition to runic power)

Runic Attenuation randomly generates 5 runic power on auto attacks, and over 45 seconds I seem to proc it about 9 times for 45 runic power. This is more straight Runic Power than Horn Of Winter, but the 2 additional runes end up being spent to convert into an additional 20 runic power (45 total) making it only come out even (not counting the damage from spending 2 runes)

In both cases, Horn of Winter comes out solidly on top for overall dps, and that's still ignoring the utility of providing its bonus on-demand instead of randomly, allowing me to combine it with important buff timings. Is there something I'm missing that makes the other two talents in this tier better? Or is this talent just underrated?

[camshlom 0]

If using ME with the Obliteration build you must be getting more than 2 procs in 45 seconds, You get 5-6 KM procs during PoF.