You can still do these quests even after your factions "turn" is over and the portal has disappeared. You just have to fly all the way there in the Eastern Kingdoms. The fastest way I've found to get there is the take the portal in the Great Seal to Orgrimmar, then in Org take the Twilight Highlands port and you'll end up right beside a flight master. Then just fly to Hammerfall, it's only one stop away. Once you're there be careful as it's the other factions turn so you may want to turn war mode off. Once you've completed the quests you may think it's impossible to turn them in as the turn in point area is destroyed and the npcs are gone. But they are actually back on the Port of Zuldazar and will accept the turn in there.