Disclaimer: in this current edit, the author has only tested this mission with mesmer. Some strategies may vary depending on profession.
In this mission, your death and Togo's death will end the mission, but all the other allied NPCs are safe to die. Instead of going straight forward, swing right as soon as you're able to, which will keep Togo from progressing his dialogue and leaving him stuck in place. It's also recommended to kill the warrior and necromancer nearby as they may wander within aggro range and start attacking Togo.
Something to note is that Zunraa is one of a small number of NPCs that can suffer death penalty, so you may want to hold off on summoning him until later in the mission so he has more health to absorb enemy damage for you in the final fights. Additionally, if you're able to preserve Headmaster Vhang to the end of the mission, it will likely help you to secure more kills on the final group. Otherwise proceed through the mission as normal. You may want to take the north path over the south path, as the south path has groups of mantids that may be trickier to deal with than the afflicted.
Once you have made it close enough to challenge the afflicted Yijo and Xeng Jo, clear a path to the south to the Zunraa shrine so you can easily resummon him. The main Guild Wars wiki shows a Zunraa shrine to the northwest, close to the gate to Seitung Harbor, but in testing there appeared to be no shrine, so the one down the south path is the most convenient with no miasma in the way.
Note: Yijo and Xeng Jo are NOT a group and can be aggroed independently. Pull Yijo off the bridge and away from his spirit, both to avoid the spirit's attacks and to prevent Yijo from getting the burn on Spirit Burn. Make sure you avoid his Spirit Rift and keep your health topped up. Xeng Jo in comparison is less threatening, though it is recommended to have an interrupt to prevent him from using Troll Unguent, or if unavailable to your profession selection, bring good self-healing, as Xeng Jo's Marauder's Shot will disable his non-attack skills on a hit.
After you have beat Yijo and Xeng Jo, you must defeat the final group in the temple, consisting of a ranger, an elementalist, a warrior, an assassin, a ritualist, a necromancer, and the monk boss Xana. Be wary of the ritualist and the monk boss, as the former has powerful spike healing with Spirit Transfer, and the latter can negate your damage and is especially punishing to weapon damage. If you're able to interrupt or destroy the spirit from the ritualist, it will make this section much easier. If you aren't making progress in trying to kill an enemy, fall back and reset. The enemies can be pulled a decent ways down the bridge, and will settle in different places between pulls, which may make it easier to secure kills.
Take out the warrior and the assassin first, this removes melee pressure and allows you to safely kite projectile attacks from the remaining enemies. Take out the elementalist next as the elementalists in this mission are notably lower level than all other enemies and easier to kill. From here you may want to target the necromancer to remove its direct spell damage, or the ritualist to remove its healing threat. Don't bother trying to kill the monk boss until you have most or all of the other enemies dead, its boss regeneration and ability to prevent damage make it extremely difficult to kill, and it will only be harder if you're taking extra damage.
If you've successfully taken down several enemies and you get to a point where you're struggling too much to make any further kills, you can consider reactivating Togo. He'll be able to survive against a smaller group of enemies, and his added damage can help overcome the resilience of the boss. Once the ritualist and the monk boss have fallen, any remaining enemies should be easy to handle.