I suppose that's due to the Pokemon you have, I never found any of the leaders that tough, since for Skyla, my Aggron and Ampharos tore her Pokemon up quite a bit. And their healing items never really matter, since if you're taking their Pokemon out in one shot, then she never gets the chance to use them. But I do favor completely offensive movesets. Also, the Skarmory has a base Defense of 140, so going for Flamethrower, especially from a Base 100 Sp. Atk should have been fine. It just depended on your team at the time, the middle Gym Leaders tend to be in that awkward not-quite-there phase for your team.