Donphan is too frail on its special side to use those extra EV anyway.
Yeah, if you only put in 10 SpD EVs it's not going to change ****, but before you posted this I thought the spread was something like 252 HP/56 Atk/24 Spe/170 Def or something.
i was changing it around a bit, sorry
[...]252 HP / 10 SpD
I thought earlier you had like 170 Def EVs wtf stop changing it goddammit.
Even running 68 SpD helps. Adamant 252 HP/68 Def is the standard Smogon spread for OU Rapid Spin Donphan and if you change those Def EVs to SpD his special bulk increases a lot. I recommend Adamant 252 HP/140 Atk/68 SpD/48 Spe. The reduction in attack may seem comcerning but here are some statistics:
Azelf and Aerodactyl are still 2HKO'd by Head Smash and Ice Shard.
Machamp is still outsped and 2HKO'd by Earthquake.
You lose some damage against Metagross but he still can't 2HKO you with Meteor Mash and you can still barely 2HKO him with Earthquake.
Swampert doesn't have a
guaranteed 2HKO against you with Ice Beam and you still outspeed and can 2HKO with Seed Bomb.
Jirachi either Tricks you, U-Turns, or Stealth Rocks and switches immediately, so who cares. For the record though, you still have a chance to OHKO with Earthquake. It's not guaranteed, but it's also not guaranteed with 200 Atk EVs.
Infernape's Fire Blast does 70% max to you, Overheat does 82% max, Grass Knot does 78% max, and Close Combat does 37% max. Even with 8% max damage from Fake Out, you'll still 2HKO with Earthquake and Ice Shard.
Roserade still ***** you, although you have a slightly higher chance to survive an Energy Ball.
Heatran's Fire Blast does 82% max to you and Overheat does slightly more than that. You have about a 50% chance of OHKOing through Shuca with Earthquake and if you don't you have a 33% chance of getting the 2HKO with Ice Shard. It's still very difficult but it's improved a lot I think.
How the **** is Ninjask the #10 lead on the ladder?
Hippowdon is where the lack of Atk EVs hurt, though that ******* is so ****ing fat that it's not like you're missing out on an OHKO anyway. Uxie is like Hippowdon in that nothing you can do to it can really hurt it that much since it's so stupidly bulky. Bronzong and Forry are in the same boat.
Tyranitar isn't 2HKO'd by Earthquake and Ice Shard anymore, but he's not that big of a threat anyway.
Starmie still ***** you. I don't think anything will change that.
Max SpA Dragonite can only OHKO with Draco Meteor if it has a +SpA nature, but you can OHKO with Head Smash if you do survive or 2HKO with Ice Shard if you feel like being not so smart. None of Dragonite's other moves OHKO you though, not even Adamant Max Atk Outrage.
Earthquake and Ice Shard will always 2HKO Smeargle.
Crobat dies to Head Smash. It also takes 35% max from Ice Shard if you want to hurt the Crobat instead of the pokemon it U-Turns into.
Gliscor is not 2HKO'd by Ice Shard or Head Smash but it never was.
Abomasnow still 2HKO's you with just about anything but you can OHKO with Head Smash.
Empoleon is OHKO'd by Earthquake if they don't kill you with Hydro Pump.
Nothing else is really that threatening.
So to sum up, this is my recommended spread:
Donphan @ Lum Berry
Adamant / Sturdy
252 HP / 140 Atk / 48 Spe / 68 SpD
Seed Bomb
Earthquake
Head Smash
Ice Shard
It sacrifices an amount of power that is ultimately trivial for more special bulk against neutral attacks.
Another solution since Heatran Overheat is the biggest concern here is to run a Heatran of your own. This would take hits from Heatran/Infernape Overheat and also take very little damage from other special attacks it's vulnerable to like Swampert Ice Beam, or Roserade Energy Ball/Leaf Storm (assuming they don't just sleep you).