Actually the different races in Qeynos and Freeport are mostly due to alliances being called upon prior to the Rending. The Second Rallosian Army threatened both cities. The entire continent of Fadewyr answered the call of their ally and sent contingents to Qeynos. Freeport was flooded with refugees that were driven there by the army conquoring the swamplands and mountain communities. Dark elves that were caught above ground when the city of Nerriak mysteriously "collapsed" during the War of the Fay had already found themselves drawn to Freeport. The Barbarians of the North were being driven from Everfrost by the advance of Rallosian races that were probably driven by the same force that started the Second Rallosian Army.
During this time the magic of teleportation had already ceased functioning. Everybody arrived by ship or foot. All of this would of taken months even years of preperation. After the Second Rallosian Army was defeated and Lucan D'Leer finally declaired himself Warlord of Freeport (after backstabbing the reminents of the Knights of Truth who came to save their beloved city) the allies of Qeynos left contigents to assist with the rebuilding of the city. Lucan would of made deals with the various other races to keep Freeport as powerful as possible, probably making deals with the new arrivals because he could be sure they wern't loyal to any of the various factions and families that opposed his rule.
Then the Rending hit. After the rending started there would be a stream of refugees heading to both cities, but all sea travel would of been cut off. More or less until the start of EQ2 nobody considered the oceans safe for travel.