My idea would probably only use the dragonstone very rarely -such as, boss battles, or if the plot required something, but for the most part would be relying on a magic tome for everyday conflict- for self defense moreso than direct combat. As for their standard stats, it all depends on which game you're referencing. In Sacred Stones, they're locked at 20. On the other hand, in Awakening, they go up to 45 and 35. Of course, in awakening, dragonstones are considerably less powerful.