I believe that the standard Calm Mind set needs Substitute.
My argument -
- It will block status ailments that would otherwise completely stop it from sweeping.
-After more Calm Mind boosts, Substitutes will begin being able to survive more hits, which will in turn allow you to activate extra Calm Mind boosts safely.
-Allows it to deal with checks on the switch, Pokemon that would otherwise be able to wall one of its attacks and hit it with a priority move for an OHKO or outspeed it are no longer a problem if Delphox can potentially KO it.
Example - Without substitute, an Aegislash can switch into a Psyshock/Psychic safely and force you to switch out due to shadow sneak, however, if you activate substitute instead of using an attack on the switch, shadow sneak will not be able to KO you and you can KO him back with a flamethrower. Essentially there's no need to predict your opponents next move and risk having to switch out your Calm Mind boosted Delphox when you can just safely hide behind a substitute.
- Past Pokemon with similar EV spreads and roles have required Substitute in their Calm Mind set (See Raikou) though Delphox needs it more for the reasons below.
- Its necessary to help Delphox deal with incoming Pursuit trappers, as substitute blocks pursuit on the switch.
-Substitute will also help Delphox achieve deciding whether or not to activate Blaze if necessary by cutting down its own HP slowly.
I think Delphox's standard set should look like this...
<p>name: Substitute + Calm Mind<br />
move 1: Substitute<br />
move 2: Calm Mind<br />
move 3: Flamethrower / Fire Blast<br />
move 4: Psyshock / Grass Knot<br />
ability: Blaze<br />
item: Leftovers<br />
evs: 4 Def / 252 SpA / 252 Spe<br />
nature: Timid</p>
<p>Substitute allows Delphox to absorb status ailments, deal with Pursuit trappers, take more hits after Calm Mind boosts, lose the need to predict on a forced switch, and trigger Blaze when you really need to. This in conjunction with Calm Mind allow it to find a role in teams as an effective special sweeper. Flamethrower is the standard STAB move of choice. Fire Blast is optional if more power is necessary and you do not mind the accuracy drop. Psyshock is the preferred secondary move of choice, as it gets around special walls that would otherwise cause it problems, has decent coverage with Flamethrower and is boosted by STAB. Grass knot is good for dealing with Water-types, but its damage output isn't very reliable as it will fail to OHKO many problematic Water-types such as Starmie. The EV spread and nature is necessary to maximize its Speed and power allowing it to outspeed threats, and be able to deal the most damage possible while unboosted. You can also opt to have an EV spread of 16HP / 252SpA / 240Spe if you don't mind being outsped by another Delphox and want just enough Speed EVs to outspeed Garchomp. The HP or Defense EVs are necessary to minimize damage from Stealth Rocks.</p>
<p>Pokemon with access to Rapid Spin are incredibly helpful. Forretress takes neutral damage from everything Delphox is weak to, can set up Stealth Rocks and Rapid Spin entry hazards. Pursuit trappers are also good at dealing with problematic Ghost-types and Psychic-types that resist its moves. Tyranitar fulfills this role well, as he resists Ghost-type attacks and is immune to Psychic-type attacks. Breloom Resists every type that Delphox is weak to except for Ghost. Hydreigon also resists every type Delphox is weak to except for Rock and is immune to Ground.</p>
<p>Checks and Counters - Tyranitar can take anything thrown at it and Pursuit it on the switch. Starmie and Greninja resist both its STAB moves, survive an unboosted Grass Knot and threaten to OHKO it with Hydro Pump. Blissey with Seismic Toss can wall sets that don't carry Psyshock. Talonflames can wall Grass Knot sets and OHKO it with Brave Bird. Choice Band Azumarill can easily take Grass Knots and OHKO it with Aqua Jet. Mega Khangaskan can break through Substitute thanks to its ability and has access to Crunch/Sucker Punch. Aegislash can switch into Psyshock/Grass Knot and OHKO it after Stealth Rocks with Shadow Sneak.</p>