Firstly, Spartans may have been the best hoplites in Greece, but the difference wasn't that huge, especially on a individual level. Much of the Spartan's efficiency came from the fact that they were almost all, as Thucydides states, officers of some kind, and that their discipline and cohesion were peerless. On an individual level, a Spartan was a very well trained, physically fit, soldier--nothing more and nothing less. In terms of personnal fighting skills, other elite units matched or even outclassed the average Spartan, and the Spartan's own elites, while certainly top-notch, were by no means superhuman, and could be matched by "normal" men. In fact Spartan society and education was not as unique as it is often made out as being; Lykurgos, the Spartan law-giver, took his inspiration from Crete, and if he added anything original it was a rationalisation of an existing system, not a pure invention.
Secondly, the phalanx is a primarily defensive formation. Phalanx battles are a slow grind until one breaks; when used as part of a combined-arms strategy, the phalanx is the anvil on which you break your opponent. The strength of the hoplites is their steadfastness, and the seeming invulnerability provided by their shield wall. They were not known for ferocious and bloody charges, but for their staying power. There's no reason why they should be the main killers in a mixed force.
Thirdly, yes, there is an inherent problem with thrusts in M&B.
.
