252+ Atk Metagross Earthquake vs. 0 HP / 4 Def Mega Charizard X: 238-280 (80.1 - 94.2%) -- guaranteed OHKO after Stealth Rock
Does nothing.
No-one's disputing that Zard X is a bad Dragon Dancer. If they were they would definitely not be nominating it to be A+. A+ is still an amazing rank full of incredible 'mon like Lando-T, Mega Voir/Lade, Thundurus, Latias, Bisharp, Clefable, Azumarill etc. All of which are very good Pokémon often considered as a first or second choice on a team because of how great and versatile they are. All that's being said is due to how many things now counter/check Dragon Dance (e.g. Mega Altaria, Mega Slowbro) or outclass WoW (Mega Sableye), it's just not quite as effective as it used to be.
Altaria might have bad speed but after a Dragon Dance it really isn't that bad. iirc the most common sets get enough speed after a Dragon Dance to outspeed at least Greninja which is really enough (correct me if I'm wrong on this guys). So 'bad speed' just is not a good argument in the case of a sweeper/cleaner, which is all Altaria would want speed for.
No-one was saying Slowbro and Sableye were fast? They were talking about Metagross, Gallade, Latias etc. whose speed tier is greater than that of Charizard's.
It doesn't need a defence stat as ridiculously huge as Slowbro's to be defensive - it's defensive stats are good enough to say the least, it's movepool is fantastic and it's defensive typing is very unique and probably one of the best for a defensive 'mon - you're REALLY underestimating it by listing it's 'common poison and steel weakness'. Might as well say Slowbro's a horrible defensive Pokémon because Dark is a common offensive type.
Look, honestly, I'd lurk a lot more before you start posting here. You've got a lot of very badly constructed and poorly supported opinions, most of which are just false or irrelevant and in general this is adding nothing to the conversation. You seem to have the opinion that a Post Count and Join Date should justify if someone's opinion is better than another's. Alright, if you wanna go there, I joined almost a fortnight before you and I have about... 1,400 posts at the time of writing this. I probably need to get a life. But I digress, even I don't post here that much unless I just see something blatantly wrong or I'm bringing up something very obvious that for some reason hasn't been discussed yet (i.e. Medicham moving down), simply because I know I really don't have enough experience to effectively add much to a big debate. I'm not touching Altaria vs Charizard and Charizard S vs A+ with a ten metre stick simply because it's way too complex a debate for me to get into at my skill level. From what I've seen, your posts really show you need to lurk more before you can make an effective comment.