Potion Effects using either an NBT editor or thrown potions or the /summon command do not work when applied to the EnderDragon
How to reproduce
Execute this command (while flying in the air):
/summon EnderDragon ~ ~-10 ~ {Riding:{id:MinecartRideable},ActiveEffects:[{Id:14,Duration:32000}]}
As you can see the ender dragon is not invisible
Confirmed in version 1.7.2