I've already been using Dugtrio in some of my WiFi UU battles.
If he can switch into a lanturns T-Bolt, it's a gurenteed KO, which is nice.
I can see anice little Mantine + Dugtrio combo happening, using Mantine to bait the electric attack, and then using Dugtrio to trap, outspeed and KO it.
Also switching into a Ninetale's Nasty Plot is risky, but it pays off.
It can also OHKO the standard Rotom set with nigh slash.
Also, which nature would be better on dugtrio?
I'm currently running Adamant, as it still ties with positive base speed 105's
I don't think Dugtrio will last in UU, to be honest.
I mean, the only thing going against it is its' average 80 base attack, but then a LO set really does make up for it.
I'm not seeing Donphan being that much better as a spinner then a Hipmontop.
Hitmontop gets access to Intimidate, which is nice. But the only thing donphan has going for it is its' 120 Base defense and attack. Ice Shard is a 5KO on bulky Altaria, so it's not doing much there.
Knock off is a nice move, if you already have a pokemon with stealth rock, so I suppose that can get annoying (lol Pory2 spec-trick attempt)
Overall, I see the loss of umbreon not that great, Dugtrio to be put into suspect just because it can trap and revenge kill too easy, and Donphan to stay in UU, as it's outshined by others (Plus plain ground typing isn't helping, weak to water, grass and ice moves, all bar ice are really common in UU does hamper it a lot)