Personally I think this is a waste of points in PVP. In PVE it's nice, it's another button to push so it's extra rage.
Stop me right here if you know for a fact that Sudden Death procs will not limit you to using 30 rage when your target is under 20% health.
In PVP I actually think this ability will make you lose. An Execute at 100 rage is a game winner in many situations. And with LK's bursty PVP you're even more likely to have a bunch of rage built up.
I'd rather not lose because I can't use an 100 rage Execute over having an extra ability when my target isn't kiting me properly. Is this the case for anyone else?
Aside: This also makes the Glyph of Execution less desirable, possibly to be replaced by Charge Glyph?