You completely ignore the consequences of getting those hazards up. In an HO vs HO match the red card lottery will most likely bring out something else that can finish of deo as HO doesnt carry walls who would fail at that, then the Deo-D player has SR up and is one mon down while his opponent can still bring his own Deo/hazard setter later to eventually get even more hazards.Aegi can still fail if the red card lottery says so, and even if it succeeds, only one side has rocks now, and it's not the Aegislash player's side. In an HO vs HO match, guess who has the advantage.
Having a Deo-D as a lead is a 100% guarantee that the opponent will always be facing an uphill battle, while you start with the advantage.
Saying Deo-D lead is always an uphill battle is just wrong, there are so many ways for the opponent to take advantage of it. And even if he cant, Deo-D dies setting up those hazards. That means most of the time you trade one mon for one extra layer of hazards as you could have used something that sets only SR but can fight after doing that. People here always act like there are 4 layers of hazards on the field for free but thats not case, most of the time it will be 2 at most and they have a price. And depending on how the game goes they might not even be worth that price, for example if they are removed 2 turns later.