In Gaelic mythology, iron is toxic to fairies, which explains why Steel is super effective against Fairy. The Poison weakness of Fairy is probably more for balance (Bug is super effective against Dark, for example).
Smogon, the premier competitive Pokemon community, has a rule against multiple Baton Pass users. Many sets also do not simply rely on stat boosting. There are choice-item sets, Assault-Vest sets (Assault Vest boosts Sp.Def by 1.5x at the cost being unable to use status moves), suicide leads, and many more. Most people also will only use one of the abilities as it is there usually one ability that is simply better.There is also Pokemon showdown, which a free battle program where one can customize Pokemon teams and battle online. Competitive Pokemon is not hard as Street Fighter.>>57
Smogon gives some good suggestions as well as what to expect, but I do not treat it as gospel. Also, breeding Pokemon does not take weeks when one has a fair number of Pokemon with good IVs (the DexNav in ORAS guaranteed one could find Pokemon like Ditto with 3 perfect IVs); it may take a few days maximum.
The physical/special split happened in Diamond and Pearl, which was huge for Pokemon like Flareon, Sneasel, and Gengar. Generation 5 added hidden abilities and the IV checker (which was made even better in the last games). Generation 6 added the Fairy type, which balanced the Dragon type, and made Steel and Poison more useful offensively.