If there's any class that strangulate needs to be used on the most, it's those 2 classes. For this ability to remain a 2 minute cool-down in my eyes, it should lock them out of using these abilities. Currently it does not.
Diminishing returns will be inplace for silences next patch (I think, or it might be the one after that). And this ability is on a 120 second cooldown, 1 bood rune, and silences an enemy for only 5 seconds at a 30 yard (glyphed 50 yard) range? I think that is less than mediocre. If there is any class that Strangulate needs to effect the most, it's Paladins and Mages.
What we really want strangulate to do is reward us with great use of Strangulate when detecting preemptively who will be trying to cast their escape move spells.
While any class is silenced, they should not be able to cast any spell, or use any cool-down spell related move. This extend to any class.
And what's with the 180 shadow damage? That's useless.