Alex Reiden
Minstrel
Codex Alera. I haven't read it, but it has legions as well as large-scale battle magic. As in, powerful mages - such as the Princeps - can wipe out cities. But usually, magic there seems to be used on tactical, spec-ops level: surgical strikes against enemy leadership and such. I might be wrong, as I said, I have not read it (yet!).
In my world there are no battle mages, because defensive/protection magic is so much more powerful that it has invalidated not just offensive magic but also firearms as well. But I do have in mind event that will change that... though that may change as I develop the world.
I have read this series and like it a lot. One of the principles I especially enjoyed was a character who did not possess magic but used cunning and tactics to overcome those who did. It was a good exercise in the vulnerability of supposedly insurmountable odds and how hubris of the empowered can become a flaw.