That sounds like something I've had happen to me a few times in different locations, so I don't think it's specific to Dragon Leap. Moving rapidly under certain circumstances seems to cause the game server to lose track and think you're somewhere other than where you see your character. The result is that your targetted attacks will not hit any target, but you can be hit over and over. AoEs will sometimes hit targets, but that's it. The only way out of it is to get out of combat, and travel to/from a different zone. It's happened a couple of times in the PD on Galen, especially running gear that gave me a movement speed boost on a kill and hitting sprint.