Not intended to be another gripe-fest, more of a wistful post. With every expansion comes change. We gain some things and lose some. Some (Volley) return again later, so who knows?
For now, what will you miss in Legion? Main one that comes to mind for me is seeing all my favorite pets out at once. I like role-playing my Troll hunter, and always imagine that Stampede represents the guardian spirits assigned to protect me by grateful Loa in Zul'Drak. If you like seeing all your pets at once, time to get that screen shot now!