Again most of us clearly state dual spec will not solve the problem. We’ve said it over and over and over and over and over again. Yet still you misunderstand or are being deliberately misleading.
Your diagram is off in many ways, here’s one.
It’s more than your post implies. Here’s another flaw in your reasoning. Each person who decides to do some dungeons as a tank or healer affects at least 3 dps who have trouble finding a group and often a tank or healer. But we do agree that it will make it easier for players to find dungeon groups and competition in arena. We just disagree with how much.