Matt,
Existing A class boats are robust IF they are built well. They seem to have about the same dent resistance as Inter 17-20's They don't take well to T-boning and when you pitchpole them in big wind you stand a chance of breaking the mast. In a year of sailing at Bristol Yacht club with about 10-12 a cats, none broke masts 1 had hull damage from a collision (t-Bone) Repaired and one had bow damage when the skipper fell off while righting it and it sailed into the rocks. The previous owner of my boat had a mast broken when someone hit him while trailering.
All and all my boat has been completely trouble free. I do not however sail it up the beach, drag it etc.

Eric Anderson