I always thought artillery in multiplayer was poorly implemented. Artillery changed the face of warfare, but not that much.
First off, you have to throw an adviser in to do it. This isn't such a big deal, but it limits flexibility a lot and makes it annoying to put artillery in your army. (Ever had problems with the Kisho Ninja? Yeah. It sucks.)
Second off, they get a ton of ammo that can just tear any army without it apart. Just keep a bunch of Yari Ashigaru to defend its flanks, and your army between it and their army, and you've got a nearly invincible machine of deathiness.
Third, even with two identical armies, both sides just wait for the canons to whittle the other one down, like you mentioned.
Fourth, the range is so freaking long. They should be a heck of a lot less accurate at maximum range, rather than having a pretty good chance to arc that shot right into your fort and hit your general's bodyguard. It's usually not that bad, but it gets so much ammunition that the enemy just waits for the RNG to give the thumbs up.
I do think it's better in campaign matches, where artillery is rare, expensive, and hard to roll to a battlefield. In that case, artillery is more of a siege and defense weapon, not one you can bring into any old battle willy-nilly.