Saladin, then likely Shaxx (but not much later), then Zavala. Remember that Saladin and the Iron Lords fought the Warlords, of which Shaxx was one. Zavala never participated in the fight against the Warlords. When he came around things had calmed down and bigger settlements started to grow. Shaxx was a Warlord himself, and still considers himself one too, so he was obviously around when the Iron Lords and the Warlords duked it out. Furthermore, in the cinematic of Zavala's past we can see Zavala walk into a young settlement in which the, then, Speaker was preaching under the traveller and in the background we can see Shaxx, not out for blood. So it's: Saladin -> Shaxx ------> Zavala