I see that you've completed it, by way of having the emblem, but for anyone else looking at this in hopes of advice - melee builds and damage resistance stacking are your best friends. For whatever reason, enemies in Avalon can still drop the boons from Season of Defiance. Ability kills can make a pool that gives you full melee energy, so you can loop pretty easily. I also highly recommend bringing a Sword and using Iron Lord's Vigor from the artefact; this is solely for the first boss, as there's not a huge amount you can do to protect yourself if Wyverns peek over the edge of the safe zone. Glacier Grenades also work well for this by blocking LoS but only really usable on Prismatic Titan. For armour set bonuses, the general consensus is to go with 2 pieces each of AION Adapter and Smoke Jumper, for easily-accessible damage reduction.