Here is what i did to pikemen - Pike Phalanx formation is divided (as before) into 5 phases. Each phase gives certain bonuses and penalties. At first, melee attack, melee damage is increased, together with bracing bonus, as time goes, this bonus is being reduced (simulating fatigue).
To make sure Phalangites are not completely invulnerable from all sides, instead of increasing their melee defense due to pikes, i have instead boosted their shield defense as that bonus is strictly directional and therefore doesnt apply from rear - this way, if you manage to outflank the pikemen, you will kill them a lot quicker (plus increased rear attack morale penalty would also play
its role). But frontally, pikemen will be extremely dangerous, so charging into pikes is really not a good idea.. Yet, they are not unstoppable force even from the front, because as fatigue kicks in with later stages, they will get less and less effective, to the point some strong melee units might get into their ranks (Legionaries) and deal a lot of casualties..