Good starting stats, there's a lot of potential for a piece like this.
First of all, the name would have to change. We already have a Jedi Knight from RotS (I know there are 2 Jedi Guardians, but I think in general it's best to avoid 2 pieces with the same name)
Maybe
Elite Jedi Knight?
The stats in general are quite high for 23 points. I'm not saying that that is a bad thing, you just have to be careful not to push them over the edge, especially with some of the available CE's.
Force 4 is also unusually high for a lower costing figure, and coupled with powerful abilities like Lightsaber Defense and Assault, give the piece a ton of power.
As is, this piece could really shake things up in the meta, it would be kinda like the new JWM. To make it a bit more balanced, I would suggest...
1) Lower the HP and defense a tad
2) Giving him Double Attack and remove Lightsaber Assault
3) Replace Defense with Block/Deflect/etc
4) Lower force to 3
If these changes were made, it would still be a useful piece (especially in OR) that could be used as intereference or beatstick support, but wouldn't become too much of a game changing piece.