You're probably thinking, "why have DAD as a fallen hero? It's broken..." or something along those lines, right? DAD is still a force to be reckoned with, and one heck of a powerhouse indeed. However, it's the way it's been used as of late that it has earned it's spot as a fallen hero.
Once again, let's look at the pros and cons of this fallen heroes, just like we did with the previous one, Mirror Force.
-Creates advantage upon summoning
-fueled by the graveyard
-can already destroy up to three cards upon initial summon
-Dark monster, so the support is incredible
-cost for activating it's effect is simple
-Likely target for Allure of Darkness now that it's at 1
-not summoned as much
-banned/restricted list lowered it to 1, making it less of a threat
-one you get rid of one, there's no more threat
-importance has lowered in certain duels
Those are my thoughts on it. By any means I'm not saying DAD is bad, on the contrary, it's an awesome card. However, it's a fallen hero due to the fact that it's not so much of a threat as it once used to be. Most of the time it will be lost to Allure (mostly because other monsters in hand are more important at the time being), or fall victim to removal or a mill from a Lightsworn.
And speaking of Lightsworn...that brings me to the idea of my next article, and my very first "Deck Analysis." Coming soon...