Vratix, I wrote up this whole treatise on EV spreads, not realizing you had lowered the HP to make Pain Split more effective. Still, I'm going to post this because I've seen many players make this mistake and I think it could do some of them some good. Also, I think the max HP spread will be better for your Misdreavus regardless.
First, I will say that when investing bulk into a pokemon you should almost always invest in HP first. Consider this the default action that should only be strayed away from in special circumstances.
If you are going to invest EV's in Def or SpD without the HP stat being maxed, then in most cases two conditions should be met:
1. The HP stat is more than double the Def and SpD stats.
2. You are going for mixed bulk rather than maxing out a particular stat.
Let me use Shiftry as an example:
First of all, we are talking about a Swords Dance sweeper, so you want 252 Atk EV's and an Adamant nature, so you can hit as hard as possible.
Next, hit a certain speed threshold. 208 will outspeed 4 Spe base 85's, which is most walls, so let's just say that's our speed of choice. This requires 48 EV's.
We are left with 210 EV's to invest in bulk. At this point, Shiftry has 321 HP and 156 in both defense stats. 321 is more than double 156, so we want to increase each defense stat until they are half the HP stat. 16 EV's a piece brings the defenses up to 160, about half of the HP. Now, in order to maintain this ratio, you need to put twice as many of the remaining EV's into HP as into each defense. To do this, put half of the remaining EV's into HP, and split the other half between Def and SpD. This yields defensive stats of 343 HP, 177 Def, 177 SpD and an EV spread of 88 HP / 252 Atk / 60 Def / 60 SpD / 48 Spe. In this case, 88 HP / 60 Def / 60 SpD is bulkier than 210 HP would have been. This is entirely because the HP is high enough to become more than double the defenses, and is made simpler by the Def and SpD being the same.
Let's look at another example, Golurk:
Again, we want 252 Atk and Adamant.
44 Spe we want to outpace Empoleon (this is a UU example I know).
we now have 208 EV's left over to invest in bulk. Lets look at those defensive stats. 319 HP, 196 Def, 196 SpD. This is really simple, put 208 EV's in HP and it's still not more than double the defense stats. This is what you will be doing 99% of the time when investing 252 or less EV's into bulk.
Now lets look at Chansey:
First, when deciding whether the HP is more than double the defenses, you should be looking at the defenses before eviolite, not after.
No Atk or Spe EV's, we are investing entirely in bulk.
Wow, that HP stat is waaaay higher than the Def or SpD stats, so we should invest in defenses before HP, right? Not necessarily. Chansey has obscene SpD even without investment, whereas it's Def can be penetrated by powerful attackers. Most often Chansey should be EVed 252 HP / 252 Def / 4 SpD, because you want to get as much physical defense as possible, which requires a full investment it both Defense and HP. This is usually what you'll be doing with walls. You'll invest in full HP and one of the defense stats in order to max out on one side of the spectrum, and take advantage of the fact that most attackers carry all physical or all special attacks. Chansey is an odd case because it's uninvested SpD is already outstanding. Usually, you will be neglecting one of the defenses not because it is inferior and not as much worth investing in, and you'd rather be a solid wall on one side than a mediocre wall on two.
Now lets get to your Misdreavus.
Again we are investing all of our EV's into bulk.
The defense stats are 261 HP, 171 Def, and 206 SpD. The HP is not even close to double either defense, so we put EV's in HP. 252 EV's later, the HP is 324. We never exceeded double either defense, so there is no reason whatsoever not to put a full HP investment in. If we were looking max defense on one side of the spectrum (we probably should), then we wouldn't care what the relative HP and Defense stats were, we'd just go for a standard 252 / 252 / 4 spread and call it a day. However, for the sake of argument, we are going for mixed bulk and want to take this into consideration.
As an arbitrary cutoff for the Special bulk we want, I'm giong to use the Special bulk of your 120 HP / 252 Def / 136 SDef spread. with 252 HP EV's already invested, 40 SpD EV's give us the same level (ever so slightly better, actually) of special bulk as with your spread. With that out of the way, we throw the rest into Def and give it a Bold nature, since it seemed like the gist of your spread was to go for physical bulk. The Special bulk is about the same, as I pointed out, so lets test a physical attack.
CB Entei Flare Blitz vs. 120 HP / 252 Def Bold Mismagius: 67% - 78.7%
CB Entei Flare Blitz vs. 252 HP / 218 Def Bold Mismagius: 62.3% - 73.5%
Overall you're taking about 7.5% less damage from physical attacks. That's nearly as much difference as between running a neutral or boosting nature. This almost certainly outweighs the benefits of making Pain Split slightly stronger. Misdreavus' fully invested HP of 324 is pretty low, anyway. Pain Split is really only reliable on offensive pokemon like Rotom who are using it on full health switch-ins and then blasting them with an attack. Misdreavus is going to be weakening things with Will-o-Wisp and with weak attacks, meaning that it will be hard to really get good use out of Pain Split anyway. You'd be better off making sure you can survive as many attacks at full health as possible.
Honestly I'd rather just run 252 HP / 252 SpD Calm or 252 HP / 252 Def Bold, though. Pick your side and stick to it, I say. With Will-o-Wisp you can cripple a lot of physical attackers, and the SpD is much higher with full investment, so that would be my preferred spread.
