If you're using the daggers for Shadow Refuge, use a staff or a bow, preferably a long bow. so you can get the while attacking bonus from it, thus making your healing go faster. you do not have to be doing any damage, just being in the attacking action.
If you are in a position where you need the extra healing that badly, you are probably stuck in melee and might as well be using your daggers for the higher attack rate and critical bonuses to energy and health.
Shiro's Blades are good because they offer Slashing dmg for daggers instead of the more common Piercing dmg. The only other daggers that hav this are the Chakrams. (not that slashing dmg is any better than piercing, but its nice to have a different type of dmg)
You guys have all been very helpful, I have one more question. These blades currently go for 60k. Will that price drop? if it does, I might sell them and then buy them later at a cheaper price...