The Continuum Blade is a very good companion to the one he has now, but only if he's willing to give up +block rating (avoidance) for a tiny bit of mana. Personally, I'd keep what he has now for the avoidance, as it's a stat that matters the most for endgame life until he decides to hit the 25-mans.
And if +40 can't be afforded, +30 isn't all that bad of an alternative: http://www.wowhead.com/?spell=22749
Okay, got the mats so all I need is to find an enchanter.
Unholy was something I placed on the weapon as an experiment and before I began to understood how a tankadin works. From the description, the proc is not affected by level and I was curious. I've come to the conclusion (apparently the same one many have come to) that it doesn't need to be because it's simply not worth it at these levels in all it's unawesomeness.