This isn't personally directed at you, Dusk, but rather to Poison Heal support in general. You just happened to bring up the best points about it so far. :P
Effective status immunity
Once CAP1 activates its Toxic Orb, it picks up virtual status immunity. This renders it immune to stray burns, taking poison damage, being slowed down by paralysis, and makes CAP1 exceptional at absorbing Spore and Sleep Powder. This helps it garner additional switch-ins, and can turn otherwise terrifying predictions into safe switches that CAP1 can capitalize on.
Status is immunity is great, I don't think many (if any) people could argue a point against that. However, the question isn't whether or not it's good or bad but rather
is it necessary? Looking at each status individually:
Sleep: Pretty much Sleep is relegated to a few things. One, Spore, which both users of it (one being more popular than the other, Breloom) are very weak to one of our STAB moves and can't do much in return when CAP1 switches in anyway. You then have Sleep Powder, which has many of the same problems as Spore: Grass-mons use them. Lastly there is Hypnosis, which has terrible, terrible accuracy problems. Sleep is "inconvenient", sure, but thanks to the nerf to a maximum of three turns asleep as well as the few Pokemon that can cause sleep, it is nowhere near as threatening as it was in previous generations, especially keeping just CAP1's typing and stats in mind.
Poison (Toxic): We already won half of this battle simply by having a Flying typing: no Toxic Spikes. However, the number of Pokemon that actually use Toxic is currently on a short list. Most of these Pokemon are slower, meaning that they can only catch CAP1 on the switch. Another point: CAP1 shouldn't really be switching in on these Pokemon at all anyway. Blissey/Chansey? CAP1 isn't going to be doing anything special to these two other than non-attack preventing moves, or maybe some gimmicky set (not going to poll jump).
Burn: This time, around 4/5ths of the battle is won with pretty much 0% reliance on Physical attacks. The 12% health loss is never a positive, but combined with Leftovers, a 6% health loss combined with a possible recovery move (assuming no PH) really makes Burns have minimal impact. I don't see this as necessary.
Paralysis: Probably the only unfortunate status for CAP1 to have, and only because of the 25% chance of not making a move. That's just annoying. However, not a lot of things faster than CAP1 run Thunder Wave (bar things like Thundurus, which beats CAP1 anyway), so once again, it'll have to hit on the switch. The speed loss isn't terrible either, since it has the bulk to survive strong attacks and the strength to KO still.
Freeze: This only happens when hit by an Ice move. I find it hard to argue that this is a benefit when Ice moves hit CAP1 for super effective damage anyway.
I think it's "cool" to have immunities to status. But is it necessary to prevent them? Absolutely not. CAP1 can easily perform its duty while being status-induced. In fact, it probably will have ways around status in matches regardless of ability.
Effective damaging weather immunity
CAP1 picks up 1/8 healing per turn, which outheals the damaging effects of hail and, more usefully, sandstorm. This means that CAP1 isn't worn down incessantly by the likes of sandstorm when switching into Excadrill or Landorus. This enables it to keep using Substitute even when in a sandstorm and not be totally worn down as quickly as it would with Intimidate.
This is a neat quirk, granted. However, just Leftovers still makes the Sandstorm damage take 0% off of CAP1. It can still do its job without constant recovery, after all. Not to mention that I don't think CAP1 will be using Substitute often against something like a pure SS team, where is simply will have the power to just KO members or shift momentum. Should it really have the ability to stay in for multiple turns to Substitute? I don't think it takes that long to change momentum. I also don't think 6% healing per turn in weather really adds anything to help CAP1 with its job at momentum changing, either. It's just a nice perk (which I understand was the reason behind mentioning this, but the point still stands).
Gives CAP1 exceptional staying power
One of the problems I see with something like Regenerator is that it only helps CAP1 when it flees from battle. This means that while out, Regenerator isn't helping CAP1 with momentum at all! Poison Heal, on the other hand, restores 12.5% per turn (after the first) that CAP1 is out. This allows CAP1 to stay out longer and keep itself healthy in the face of Pokemon that would love nothing more than to steal momentum away from it.
Here's where the red alarm goes off for me. When I see the term "staying power", I immediately shift my mind to read it as "wall", which is not what CAP1 should be striving for. Skarmory and Gliscor are known for staying in multiple turns in a row to either wall attacks completely or set up strategies and sweep. They are the exact opposite of "momentum", regardless of how vague the concept actually is. CAP1 should be focusing on shifting momentum the second it's switched in. Intimidate was chosen for that very reason, and I see no reason for Poison Heal, as it encourages the opposite.
Isn't broken on CAP!
We could easily make Poison Heal the DW ability to allow us to force it to have some move illegalities when using it if you're worried. These illegalities might include moves like Roost that would otherwise be exceptionally useful in making CAP1 nigh impossible to kill with Poison Heal. For this reason, we really won't have any issues with a brokenmon by using Poison Heal, and we gain the full benefit of a CAP with great staying power.
In my opinion? No, this is not 100% guaranteed to be broken, and there are ways of hindering the ability so that it doesn't get that broken. In truth? No one knows if it will be broken or not, and it's impossible to prove for or against its brokenness until we have concrete results. I personally wouldn't give this as a positive.
However, we must also realize what will be made if this gets Poison Heal. Gliscor is exactly the opposite of a "momentum-based Pokemon". It got Poison Heal, but also was restricted greatly by having it be incompatible with Roost. To be frank...that's probably the best we'll do in terms of limiting movepool options, with the exception of disallowing moves that cause certain status effects. Now, let's compare Gliscor to CAP1, since while their goals are not very similar and their typing is off, it's important to understand the bulk of CAP1 compared to Gliscor and the role it plays currently.
Gliscor:
LO Salamence's Outrage:
61.0% - 72.0%
Leftovers Gengar's Shadow Ball:
46.9% - 55.4%
CAP1:
LO Salamence's Outrage (not factoring in Intimidate since its PH):
66.7% - 79.7%
Leftovers Gengar's Shadow Ball:
38.4% - 45.2%
In conclusion, that means that Gliscor is taking just
5.7% less damage from this neutral Physical attacks, while CAP is taking
8.5% less damage from this neutral Special attack. They are slightly similar, yes, which is my point:
what is going to stop CAP1 from simply becoming a Special-oriented Gliscor? It has similar Physical bulk, and better overall bulk. It might have its moves restricted, but it will still be able to tank just as well with a 12.5% health increase per turn, combined with a *likely* Protect. There's nothing right now that's telling me that it won't just turn into a Gliscor-like Pokemon, no matter how many moves you ban from it. Which, by the way, I feel too many banning of moves would simply mean that we're just trying to make excuses for Poison Heal to work.
Contrasts excellently with Intimidate
Intimidate is an immediate boost (or drop, as it were) on the switch, which allows CAP1 to really force switches. Poison Heal, on the other hand, complements a different playstyle completely by not affording as much up-front oomph and instead focusing on keeping CAP1 out longer and with higher total HP. This is pretty much the ideal balance we want for our abilities, especially if we'd like them to not be relegated to comments like: "Man, why would we EVER use X over Intimidate?" I know I would use Poison Heal over Intimidate on some builds.
This ties in to the "staying power" post. Why do we want CAP1 to constantly stay in and become a wall? How does that gain momentum? It instead creates or loses no momentum whatsoever. We don't want this thing to be staying in for 5-7 turns and walling things to no end while healing 12.5% every turn. It'll just be another Gliscor / Skarmory.
In response to the last part about the relegation...is there really a reason why CAP1
needs to have two amazing abilities so that they balance each other out? Intimidate already does an outstanding job at what it does, and IMO abilities like this promote the opposite of what we're aiming for. We need to find an ability that compliments Intimidate's goal, not encourage a playstyle opposite of it. No matter what we do, there will always be a dominant ability and a major set (unless we were to make this like Salamence and unpredictable, which is not what we're aiming for).
A fair compromise would be something like
Overcoat, which has all the perks of weather immunity (that means Leftovers damage in weather) minus unnecessary status immunity and staying power of 12.5% healing.
I think that in order for me to accept Poison Heal for CAP1, there needs to be proof that it's not going to end up as a Gliscor-esque wall. The typing and stats already point towards this, and we can only limit movepools so much before simply just making up excuses to fit an ability.
