It's more or less a matter of convenience. It's not like an alchemist where you don't need to get an elixir alchemist to get the flasks. [though you'd get the most profit out of using an elixir alchemist] With this stuff, you're required to find either one or the other. It's completely unnecessary.

This is also one of the first cases where a class's DPS is reliant on another person's raiding simply because of professions.

They've done buyable ammo for reputation.
They've done crafted ammo through engineers.
But it just seems odd to combine both reputation and a crafting profession to create this new tier of ammo.
And it's even more odd to use a specialization system that doesn't really get much time in the sun these days.

Yes, things come at a cost, but it just feels like such a hassle that a Hunter Engineer, if they wanted to keep their ranged weaponry in check, would be forced to switch to another specialization.

It's not "dumbing down" the game. It's making things more complicated than they really need to be. And the idea that making it so that ammo is able to be crafted by all engineers is going to cause Blizzard to require they give us max level characters with full tier for free is such a crappy argument.