RDM is extremely easy and forgiving of mistakes. It has significantly higher mobility, survivability, and a lower entry point to perform well.

BLM does higher damage in dummy-perfect combat conditions, but minimally so, and the slightest bit of movement cancels that advantage.

It depends why you are struggling with bard, but BLM certainly isn't easier than bard. They have significantly less buttons to press, but the punishment for screwing up or not knowing mechanics is very high.