Ardenweald > Heart of the Forest > West End (external to tree) > Quest-giver: “Training in Bastion” icon appears nominally on the mini-map, but player is unable to interface with the NPC (does not appear). My character is mid-way through the Chains of Domination quest chain; may be a phasing issue?
That could very well be the issue. When NPCs aren’t where are supposed to be it is most likely due to phasing. Finish the Covenant quests you have and check back on the NPC.