I've been working on a mod/addon to make ores generate in the end. I've looked around, and found a hook that used to be in it, but the way to add to the list of blocks seems to have gone away. If anyone has found out how to do this without changing any classes but my own, I'd appreciate if you could tell me how.

I haven't tested this specifically with the Ender Dragon, but I'm pretty sure this is what you're looking for:

// in your Block class, add this method:
@Override
public boolean canEntityDestroy(World world, int x, int y, int z, Entity entity) {
return false;
}