Well, the assassin-faithful cults would be much weaker due to such a big loss. Basically, more recruits and prestige but fewer masters and handed down teachings/techniques. I don't want the Forsworn to have 5-9 unique units, but there will be a deficit of them for at least 2 turns, depending on the sustainability of the impact.
Remember, each Iron Lancer is worth a lot, each Lance Point even more, and each General even more, and the Iron Prophet is the Best General and Spiritual Leader, with as high authority as the Arch Faelinkrisr dwelling in Nessos.