No, I avoided it because it's entirely useless.
Once you get near perma-energize and have accolades you (shouldn't) have to worry about recovery. Or at least that's the case on a Stalker, 3 brutes, a Sentinel, and a Tank.
As a debuff, at least in regards to melee classes, it's also pretty useless. Okay. Fine, assuming for a second that you slam it into ED cap a single pass will wipe around 80% of a target's endurance bar. GREAT!
If you slam it into recharge cap as well you can roughly knock off 80% of your target's endurance every 18 to 20 seconds.
Slight problem: for the most part unless you are cranking elec/elec, you probably don't have any way to KEEP that endurance off. You need powers tagged with Recovery(T): (minus).
If you don't have that, simply wiping your opponents endurance won't actually change anything. Enemies will still be able to attack, so you just rooted yourself for 2.03s... for... what?
Taking up a power choice that could be used for anything else? Dumping slots into a power that really can't actually help the other powers selected?
This is why actual builds dump [Power Sink]. It's a great power if you have no IO's, and if it was an earlier selection than level 35 it make make sense for a mid-range build, but once you get into a final build, it's just not a viable choice.
Now, as to the knockback question, there's often a bit of confusion. You can have all the knockback protection in the world. I rule-of-fived knockback procs on a Fire Aura with 4 Gladiator's armor, one Fury of the Gladiator, 3 karma's, 2 kismets, and an Overwhelming Force. Total KB protection of 39.
That fire tank STILL got knocked around... because despite having silly amounts of Knock Protection... there's no knock resist.
Electric has kind of the same problem. You do get knock protection in [Grounded], but you do NOT get knock resists. The result will be that no matter how much more knock protection you add, enemies who can knock you back when [Grounded] is in effect, will still knock you back.
Interestingly, while [Ageless Incarnate] will give you Defense Debuff Resist, it won't give you knock resist.