Quoted By:
Mega Altaria
HP 140 (+65)
Atk 70
Def 115 (+25)
SpA 70
SpD 115 (+10)
Spe 80
Type: Flying
Ability: Filter
Description: That's right a Mega Evolution that LOSES Dragon type. Madness! Instead of becoming more dragon-like, Altaria's Mega-evolution would turn more and more of it's body into a cloud, making it's form fluid and allowing it to let damaging blows pass right through.
Explanation: Altaria is already a good Pokemon. Dragon Dance + good defensive stats makes him a good physical attacker and his movepool makes him awesome with Choice Specs. But the problem is that despite his great defenses he's super vulnerable to Stealth Rocks and three of the most dangerous attacking types; Ice, Rock and Dragon.
Altaria's loss of the Dragon type and the gaining of Filter instantly makes it a much stronger Pokemon by strongly mitigating it's vulnerability those three super common super effectives, as well as it's new vulnerability to Electric. This strong defensive gain is balanced by the loss of Dragon-type STAB, as well as Dragon resistances and it's valuable Natural Cure ability, but it's new very high HP stat and continued access to Dragon Dance will keep these vulnerabilities from being too crippling. Stealth Rocks remain it's biggest threat, but with high defenses and HP even with a missing 1/4th off it's healthbar Altaria is not dead in the water, and with such good bulk combined with Dragon Dance running Altaria as your lead would be a viable way to reduce SR's impact on your plans, especially if you find room for Defog in your moveset.