Even PT 5 and 100-ish wpf can be a devestator in strat as long as the commander remembered to bring rocks. They don't slow down the army (one troops can carry 8 stacks), works well against low armoured targets, stunning archers are great fun, makes you able to stop kiting/retreating enemies. Besides, there's nothing you can do in a shieldwall as a shieldless melee anyway, so why not launch some rocks? Wreck some havoc and all?