Honestly, even when I'm Heavied I just keep going on my mount and ignore the mobs. And when I'm on my WHM, I dismount, Esuna, Dash and remount once I'm clear. It's one of the most nonsensical designs of this game. The mobs are so trivial that they don't pose any danger, making the Heavy debuff just an annoyance and nothing but an annoyance.

If by the Heavy debuff I face the danger of death, then the debuff would make sense. But now? I can only attribute it to an inexplicable moment of enlightenment on the dev team. We'll never understand it, and we'll probably never understand why it will remain in the game for ever and ever.