Honestly, the only thing that made air anchor suck was that it wasn't INSTANT death, you had to wait til its next turn for it to die and there's usually plenty of ways to kill anything weak to it in a single turn (and every thing it works on, it works 100%, actually)
That aside, they were removed for their 'death' properties... when the person said they don't do anything for the challenge, I'm pretty sure he meant they lower the difficulty in a way that breaks the spirit of his challenge game since he was unable to tweak them to remove these properties.