Guys, legionaires carried two types a pilum, they have a lighter one for throwing and a heavier one that could be used as a weapon as well as thrown. One of the formations recorded by Apian was one where the front couple ranks knelt behind their shields with this second heavier pilum braced into the ground. This would deter cavalry charges along with their prepared formation. However, cavalry would still make mach charges to try and unnerve the troops so whenever the cavalry would get in their face, the legionaires in the back would just pilum them.

The issue is that as of EBI, fresh legionaires in formation and guard mode get slaughtered by cataphracts from the front with the cataphracts taking very few if any casualties.