Tier 1?
ehm... what? Entire legion, enhancement shaman was definetly not tier 1. Elemental was more or less useless on the start of legion expansion (7.3 it was tier 1, i agree).
Elemental was unplayable entire WoD.
And now? How often you face elemental shaman in arenas?
Resto shaman has utility, that is corect!
But has no mobility, hasn o bubble, has nothing to survive stun... Its i would say well balanced equation. For average player, the resto shaman is probably the worst option. For skilled person its with druid tier 1 healer on current meta.
Aoe stun for shamans - its just illusion, its really hard to stun good players and you need to prepare setup for it.
Hex is fine, unfortunatly its only defensive tool, because you face manymanymany resto druids and even tooltip say its usable against beasts, it doest work on druids (if he is not blind).
==> So all is left are roots. And if u r enha you have very often ,,nothing". (against good players, hex or capacitor are strong in BG or against mediocre players)