Consider activating it before moving forward. There is another Waypoint Portal in the northern section of the swamp, and that Waypoint Portal may be closer. The Source Temple and the path to it are north of the swamp and east of the Phantom Forest North Waypoint Portal.
Consider retreating back to a city after every other encounter to repair your weapons and armor you don't want to be in the middle of one of these fights when your equipment breaks. There are a lot of enemies along the way, and each encounter features a minor boss. If you handled the Death Knight patrols, it's time to start the gauntlet toward the Source Temple. It's unlikely your mages will be targeted, especially if you use your front-line fighters to block the way. Physical attacks are all they can do, and they also tend to attack whichever of your party members is physically closest. However, as you fight them, it'll become easier and easier as you get used to the technique. The first time you have the fight, it may feel a little intimidating.
