Remove thier secondary weapon, then lower thier attack speed.
Code:
stat_pri 9, 3, no, 0, 0, melee, melee_blade, piercing, spear, 25, 1
to
Code:
stat_pri 9, 3, no, 0, 0, melee, melee_blade, piercing, spear, 300, 1
Charging them is still suicide, and frontal attacks are of limited effectiveness (not uber like you want, but still tough for all but the most elite) because you still have all those pike pushing you back. But once they are engaged they are quite vulnerable to flanking attacks.
They can still turn way too quickly for a flank attack to be very effective if they are not already engaged, but it's the best I can offer atm. Aditionally they are not very effective at killing except on first contact, so anyone fighting them from the front is in for a long fight, so your not going to be able to just spam a line of pikes and crush your enemy in a full frontal assault (like you could in Rome) but with proper support they are very effective at holding a line and keeping enemies occupied.
Also, personally I remove the 'phalanx' formation as well.
Now that I think of it, I have not really played with Vanilla stats in a LONG time, it looks like you may need to lower thier attack some too.