Sks has not only been bad as a stat because of the TP drawbacks, but because it requires so much to give so little in return and hurt what the other stats could have given you, specially Critical Hit... I really dislike that one...

Gnashing Fang having a 35 seconds CD would make one think "hey, I want it to be down to 30 seconds", but for that you would need enough SkS to reduce your GCD to 2.14... that is not feasible unless you have a 10% Haste buff at the very least...

So, no, I don't think SkS will be required for more than the 2.4 GCD mark (and even that much sounds like too much).

SE is too scared to go faster after all.