Bisharp is the most viable of the four right now, and as such it doesn't need a lot of improvement. It should probably be taken in a different way. I was thinking about adding a lot of speed, but I'm really not sure about what else. Dark/Steel is a great defensive type, boasting 11 resistances and only 3 weaknesses, so an increase in bulk would really help a rather frail Bisharp take hits better. Swordsman sounds like a great idea, but if I'm correct, no Steel-type attacking move is affected by it, and I'm pretty sure only Night Slash is its only Dark-type move benefitted by it. It seems like a great idea flavor-wise, but it isn't really that helpful and probably worse than Defiant.
Druddigon definitely needs another type. I was thinking maybe Dragon/Fire, as Druddigon needs to keep his body temperature warm in order to stay mobile. It also gives Druddigon an immunity to Will-o-Wisp, which is very important for a slow, bulky attacker like him. Fire is also a good defensive type when paired with Dragon, as it removes two of Dragon's three weaknesses, and Dragon removes Fire's weakness to water. Druddigon also has a couple Fire moves already, but I think adding another stronger physical Fire-type attack would be best. As for ability, I'm not sure. Druddigon has lots of coverage moves with low base power, so maybe an ability that can boost a lot of them like Tough Claws or Strong Jaw (although Tough Claws makes it a lot like MegaZard X).
Bouffalant is totally getting Rock Head Head Smash. It's just dying for it, what with its ability to derail a train with just its head, and this quote from its Black Pokedex entry: "Their fluffy fur absorbs damage, even if they strike foes with a fierce headbutt." This implies that even after hitting someone or something at full force with its head, it feels no repercussions whatsoever. Bouffalant's moves are very high-power, so missing out on the extra boost from Reckless won't be too much of a deal, especially with Head Smash. In fact, with its increased survivability, Bouffalant can take advantage of its already good 95/95/95 defenses. (Mew King basically said this already but I was typing this before he posted so)
Druddigon definitely needs another type. I was thinking maybe Dragon/Fire, as Druddigon needs to keep his body temperature warm in order to stay mobile. It also gives Druddigon an immunity to Will-o-Wisp, which is very important for a slow, bulky attacker like him. Fire is also a good defensive type when paired with Dragon, as it removes two of Dragon's three weaknesses, and Dragon removes Fire's weakness to water. Druddigon also has a couple Fire moves already, but I think adding another stronger physical Fire-type attack would be best. As for ability, I'm not sure. Druddigon has lots of coverage moves with low base power, so maybe an ability that can boost a lot of them like Tough Claws or Strong Jaw (although Tough Claws makes it a lot like MegaZard X).
Bouffalant is totally getting Rock Head Head Smash. It's just dying for it, what with its ability to derail a train with just its head, and this quote from its Black Pokedex entry: "Their fluffy fur absorbs damage, even if they strike foes with a fierce headbutt." This implies that even after hitting someone or something at full force with its head, it feels no repercussions whatsoever. Bouffalant's moves are very high-power, so missing out on the extra boost from Reckless won't be too much of a deal, especially with Head Smash. In fact, with its increased survivability, Bouffalant can take advantage of its already good 95/95/95 defenses. (Mew King basically said this already but I was typing this before he posted so)