One aspect of the Battle of Pydna which has always struck me is that despite being pushed back through hours of heavy fighting, the Roman maniples suffered negligible casualties against the Macedonian sarissa phalanx.
Does this mean that the sarissa phalanx was basically less than lethal? I think it does.
I believe that it was nearly impossible to perform a lethal thrust with the sarissa.
Even if the wielder is able to generate enough muscle power to get the pike moving forward at a lethal energy level, that energy will be lost in the flex of the pike as it accelerates and when it hits home. In other words, the sarissa of the Successor kingdoms (which was longer than those used by Alexander) was essentially a non-lethal weapon.
Of course, we all know that the impractical length of the sarissa was due to an arms race between the Successor kingdoms to see whose phalanx could out-reach whose. It was never meant to fight non-phalanx heavy infantry.
Had the Macedonians decided to opted for dory-length spear instead of pikes, could they have done better against the Romans? The dory armed hoplite phalanxes of old were able to defeat their Persian non-phalanx adversaries without the use of cavalry or flanking maneuvers.
A 3-meter or shorter spear like the dory is much easier to wield and thrust with. The fact that the hoplite phalanx was doing almost all the killing in the Classical period means that it was quite lethal all by itself. In the Hellenistic period, the sarissa phalanxes rarely decided battles, that role was left to the cavalry or to flanking maneuvers.
In the pike and shot age, the lethality of the 3 meter pike was again proven. Pike squares were devastating when matched head to head. And against non-pike formations, the pike squares were unstoppable, even without cavalry or musketry support.