it's ok all you have to do is run balloon tran with magma storm taunt toxic but then miss anyway like i do every single time vs stall
I would really hate to have to start running Shed Shell on things like Magnezone, Charizard-X, Rotom-W, etc
It's
ironic that Mag has to be the one running Shed Shell.
Also, I'm hoping that you just forgot that Megas can't have hold items, and that Rotom isn't grounded, and thus cannot be trapped. Mag and Heatran are probably the most vulnerable when I think about Dugtrio in OU.
The only for-sure method that I can think of for beating Sableye Dugtrio + Stall Friends is Air Balloon Heatran (with Magma Storm, Taunt, Toxic). (And by viable I mean it's not just some counter-team thing that only works vs one playstyle and gets blown away by the rest)
I haven't played vs Dugtrio stall that much myself, but I feel like you can play around it (though very very hard). For example, your opponent knows that you're going into Heatran, so you stay in (assuming you beat Dugtrio, like Keldeo vs their Amoonguss or something) or switch into something that pressures his Dugtrio instead. To beat stall you already have to outpredict or cheese, so you just have to outpredict more I guess.
I don't think Arena Trap is too broken. Its presence does mean that you have to think a lot before you move. But it also makes your opponent more predictable (assuming he/she's not stupid and thinks Amoonguss beats Heatran or something). If you make the right predictions you can still win versus it (given that your team isn't complete garbage). If your opponent outpredicts you then you would have lost regardless of what team they were using.