You can hold groups of 9+ mobs in wp using just flash spam with SoS and SW as they come around and Riot blade combo to keep flash going.

You don't even need to use Harlone combos.

This is with full DF and relic gear on the PLD. You can hold more if your group is geared with you.

Before that, when you're only geared to take each group as they come (2-3 mobs at a time, perhaps 3-5), the exact same tactic can be applied.

Flash spam will hold aggro perfectly.