Quoting Chibiabos, reply 8Without Shrink, dragons would be unassailable until you could cast Diamondskin.
There's also blindess, or you can have a dragonslayer marksman + champion' lance + giant form double-strike the dragon. I've had my Verga kill dragons with one shot, and he did not have access to life magic.
Blindness seems to not be working, as reported by another user.
And you must be fighting different dragons than I am, because every dragon I face has initiative such that they get 2-3 rounds for each of my archer's rounds unless I manage to cast Slow on the dragons and Haste on my archers and, hey, Shrink (and I am not allowed to stack Shrink) and a tank (a tamed Corpse or more powerful spider is my tank of choice, often) really, really helps.