I could be wrong, but I don't think that the use of blood in magic makes it blood magic, you have to use blood to power the spell for it to be blood magic. I am opposed to phylacteries so don't think I am trying to justify their existence, but I don't think the blood powers the spell, it just allows for the tracking.
The darkspawn blood used in the joining is magically altered, I don't think it is used to power the spell.
"Phylacteries, ironically, are a form of blood magic.[2] When a templar wishes to track down a fugitive mage they will use the phylactery as a way of homing in on the fugitive by way of a "hot and cold" situation, i.e., the phylactery glows, becoming brighter the closer it gets to its respective mage.[3] If the mage dies, the phylactery will no longer glow.[4] It can be even used to remotely cast a spell on its owner mage.[5]"
http://dragonage.wik...wiki/Phylactery
"In the Warden's Keep DLC, the Warden learns of an ancient Grey Warden mage named Avernus who utilized blood magic to manipulate the darkspawn taint used in the Joining (the Joining itself being a form of blood magic)."
http://dragonage.wik...iki/Blood_magic