I think you guys are underestimating agro-Donphan. I have done some major testing with it, and it has pretty good matchups. Here are the decks I have playtested against:
Reshiboar-not a favorable matchup-but definately winnable. Reversaling up the emboar can cause major pains, as Reshiboar doesn't really have room for switch. I would say 40-60 Reshiboar.
Magneboar-A pretty favorite matchup-reversals come in real handy here. I usually am able to get a major prize lead, and continue to one shot magnezones with pluspowers. RDL could be trouble, but I've never really gotten it out and powered in this matchup. 60-40 donphan
Zekrom-mostly favorable-this matchup isn't as good for donphan as people think. Agro-Donphan plays very few basics, so can be donked pretty easily. If you make it past the donk, though, donphan is able to sweep. 65-35 donphan
Donphan with Reuniclus and serperior-this was my hardest matchup. They set up pretty easily with cleffa, and I have to burn a lot of reversals to get around its body. Even if I'm 4 prizes ahead, when they set up, I can't damage them, and so have to rely completely on reversal. Easily 30-70 them.
Yanmega Tech and Deck-this card is really overrated as a counter to donphan. I was able to beat the tech every time. In a full yanmega deck with counterstadiums for my ruins of alph, I still won. The problem stems from the fact that yanmega fails to attack consistenty, especially as a tech. There were many time I had a different amount of cards and no copycat or judge, even though I ran 4 of each. Constant SSu in donphan helps a lot, too. 70-30 donphan
In theory, Lostgar should be a pretty easy matchup, with so few pokemon and 4 junk arms. However, a nailed lost zone could be painful. I haven't tested this matchup, but it seems pretty favorable. 65-35 donphan
Dark and cinncino decks seem like an easy matchup, with me OHKOing them for 1 energy while lasting multiple hits, especially with ssu. I haven't tested this matchup either, though. 80-20 donphan
Still need to test against donphan machamp and any water variants, but things look pretty good for agro donphan. Do not count this out so easily.