Summary
Blood magic is “unlikely” to be a specialisation in anotherDragon Agegame, as the lead writer feels that it’s too “nasty” for a hero to use. This is despite blood mage abilities being available in bothDragon Age: Originsand Dragon Age 2, before disappearing inDragon Age: Inquisition.
In response to fans, lead writer Trick Weekesarguesthat blood magic has become “key to a lot of nasty stuff” since Origins, and is “not a road [they] want the hero to walk”. They argue that this is because Dragon Age 2 and Inquisition have featured more examples of it being used nefariously and with the blood of others, not the individual magic user.

Dragon Age Won’t Bring Back The Blood Mage Specialisation
Weekes' explanation comes in response to a fan asking if old subclasses that haven’t made it intoDragon Age: The Veilguardcould be featured in future games, including blood magic.
“Blood magic is unlikely because we’ve shifted it from a power boost to really being the key to a lot of nasty stuff we aren’t interested in having heroes do,” says Weekes. “I think it can be ethically neutral if you only use your own blood, but after seeing it used as a required part of mind control and demon binding in [Dragon Age 2] and [Inquisition], it’s just not a road we want the hero to walk right now.”
With that said, blood magic has always been considered controversial in the world of Thedas. If you play as a mage in Origins, your introduction to blood magic is through your character’s friend, who is scheduled to be made Tranquil (pretty much the worst thing that can be done to a mage) because he’s suspected of using it. Later in the game, the Circle of Magi is overtaken by blood mages who the player is tasked with defeating. You can also choose to use blood magic yourself if you’re a mage.
Mechanically, blood magic worked by letting you sacrifice health in place of mana. Weekes says that this feature could return - it just wouldn’t be blood magic.
Similarly, Dragon Age 2 established blood magic as being dangerous and feared. One of your companions, Merrill, was a blood magic user, and it ostracized her among both her pro-mage and pro-Templar peers. However, she was shown to be using it with good intentions, establishing that not all blood mages are disturbed and power-hungry. Again, the player could specialise as a blood mage if they wanted to.
Many fans are disappointed that The Veilguard - and presumably other future instalments - won’t let players choose to become a blood mage. Of course, choosing to engage in morally dubious behaviour has been part ofDragon Agesince the beginning, so some a fearful that this means The Veilguard will make it harder to roleplay.
With that said, we’ll see for ourselves soon enough. Dragon Age: The Veilguard is set to launch this autumn.