Okay, more about the tier changes...
I can understand why Dugtrio got bumpped out of OU. I honestly don;t know who's ideal to put it there to start with were, but anywys, why was Donphan placed into UU? I have one that works wonderfully for me on my OU team. Is't he sort of too beastly or the likes of UU?
Please please PLEASE read this before making any more questions about "Why Smogon put x in tier y." There is a perfectly explainable reason. Besides, what is wrong with Donphan in UU? It has no reliable recovery, meaning even weaker Physical sweepers will eventually wear it down. There are many powerful Water-types that can take it, Azumarill, Milotic, Lanturn. It doesn't beat Moltres or Migmagius either. Personally, I like the introduction of Donphan to UU, it is a perfect switch-in to the ever-present Registeel and so, I believe, will help to diversify UU.
Good in OU =/= Too strong for UU. Ask Tentacruel.