Gotta go with the "Wait 10mins (obviously exaggarating but you know what I mean) before pulling a boss/group of mobs/what have you".

Other than that nothing really comes to mind that hasn't been said. What can I say, heavy's prettay annoying and to be fair I don't see why it's a thing on your mount. Indeed, your mount exists to get from A to B faster, so why in Bahamut's name do we get slowed by nearly every attack that hits us while mounted?!