On Rock Blast vs Stone Edge: Because of the way Rock blast works, it actually has a 33% chance to be as strong or stronger than Stone Edge (4-5 hits is stronger). When you factor in the extra 10% accuracy, as well as the increased critical hit chance (more attacks = more chance for a crit, and a 3 hit Rock Blast with a crit is equal in power to Stone Edge), Rock Blast will, on average, produce around the same amount of damage. It may let you down on a crucial occaison or two, but so does Stone Edge's accuracy. Rock Blast also has the advantage of beating Ninjask, and other Focus Sash users, which is always nice.
Anyway on a more offensive Armaldo, I would probably be running some sort of Speed. 128 HP / 252 Atk / 128 Spe lets you outrun minimum Speed Tangela, which is a decent benchmark to aim for. I would also prefer to run 3 Attacks + Rapid Spin, and leave Stealth Rock to something else, as Armaldo gets no where near as many chances to use both Stealth Rock and Rapid Spin if its offensive. 3 out of X-Scissor, Rock Blast, Earthquake and Aqua Tail would be my choice, depending on what threats I needed to hit (Aqua Tail for Golem, Earthquake for Probopass etc).