These are really good points from an archetype perspective and it makes sense from an Issue 1 legacy standpoint, but looking at the cross-archetype powersets and the availability of IO sets, procs, and Incarnates, it starts to become less driven by those things you've pointed out. There are varying degrees of success in each AT filling each other's roles and none do so as well as the specific AT - but it's less relevant now than in years past. That's just the state of the game.