Don't think there's really much to debate. It's a strong unit with some big situational advantages. Would the game be more or less fun if you removed all such units? For me the answer is, less fun ofcourse. As long as there's a bunch of viable strategies and army line up's I don't think any devs are wasting their sleep over it.
On a related note, I disagree that the female ruby army (dryads+lake fairies+sprites) lose their power in demonis+labyrinth+final fights. With sacrifise and resurection all these fights where all a breeze without losses apart from the final fight which did make a pretty heavy dent on the army but it's the last fight and was never a question that I wouldn't win the zerg fest so not really that bothered
note: If anything I think the last fight versus only lvl5 was probably the most boring fight in the entire game with zero strategy chooices just zerg zerg kill kill.