Such a huge wall of text, which could be replaced by one line: "Despite being "redesigned", we're still in 2004, while all other specs are in 2016". That describes the situation perfectly. Shadow priest is absolutely amazing - if you place him into a WoW of 2004. In a WoW of 2016, where encounters require short bursting, quick autocleaving, mobility, burst selfhealing tied to dps abilities, and smart playing with defensive and offensive cooldowns, shadow priest looks like it lacks everything I listed. (also: no, pressing stm and burning through your keyboard is not a smart playing, smart playing is tying your short bursts to your trinket procs).
I really see no sense in comparing shadow priest to enhancement, because people who were remaking enh were doing it for realities of 2016 wow, not 2004.
Also, about orbs. I admit, I laughed. We're immobile as f**k, so let's make us move even more.
We were crap in wod's dungeons, and will be even worse crap in Legion ones. We were somewhat good in raids in WoD, we will be somewhat good in raids in Legion. Like, you know. When you're a brilliant shadow priest player surrounded by mediocre players, you will be #1 always. When you're surrounded by people of same skill, you will be in the upper middle. Like it always happens when it comes to shadow priest.