Question, when doing undercity once you get to lvl 4 attunement is it necessary to get the remaining tributes? Also, is it important to destroy the weapon or armour depots on the map too?

You can stop the moment you reach attunement lvl 4 and head to the portal bro.

the only reason to pop more is if you have the goblin tree from war plans and have a chance for more goblin spawns (however it isnt worth running out of time for)