When you do /entitydata @e[type=EnderDragon] {HealF:0s} that kills the dragon but the dragon gets stuck on its death animation and never dies
When you do /entitydata @e[type=EnderDragon] {HealF:0s} that kills the dragon but the dragon gets stuck on its death animation and never dies
Per @unknown's comment:
Please do not report issues related to NBT tags as bugs. If changing NBT via commands does not have the expected effect, that's always considered "working as intended".