I like to think of it as "silence" given permanency personally.
If that was the case then blood magic as well wouldn't be an effective measure given it negates all magic, blood magic or no.
There just has to be some logic behind it, something an author thought about.
For example In D&D there are spells that require verbal and somatic components and being bound or gagged will disrupt those, but there are also spells that don't require those and they can't be stopped. Then there are dead magic zone that have no wieve to draw spells from, but then again there are for example psionics that are their own wieve and their spells work inside dead magic zones. So when you get to the bottom of how things work you understand what works where and why.
There has to be a specific way about how these runes work in DA, what exactly they do to a mage.
Like for example - what the hell is silence?