Gibson.3517

....Attemp 5 - cleared all mobs from instance before talking to Tonn at the start. A few risen spawned after third tower exploded, but I could speak to Tonn afterwards and complete the quest. Thanks Averios.6012

Yup, this quest is very broken. Just returned after 4/5 years and encountered this disappointment. My experience:Attempt 1 (grouped with 1 friend) - Tonn would not blow up third tower.Attempt 2 (grouped with 1 friend) - Tonn would not blow up third tower.Attempt 3 (solo) - Could not speak to Tonn after clearing the beach objective completes and cutscene played.Attempt 4 (solo) - Made sure not to kill Krait until after the third tower was destroyed as suggested on wiki. Could not speak to Tonn after clearing the beach objective completes and cutscene played.