Vanguards are not bad at all, I'd say. They're tough, have lots of room for missiles and torpedoes, one of the faster frigates (and very fast when burning forward, which is useful for capping points), and the lack of shields means that you can safely overflux them with lots of dakka
The dampener also more or less acts as a safe flux vent for the ship.
In addition to all of that, they have lots of OP for hull mods, so you can stack armor, add missile racks, or SO, or whatever you might fancy without sacrificing much.
It's overall solid, and doesn't die as often as I first thought it would.