Bonus Stability question

Is it worth it to fill out that bar or just hunt down the Echoe objective and open portal right away?

General answer: No

Depending on the layout, if the density is very high and you do have some more enemies around when completing the objective you can definitly stick around for a couple more mob packs before leaving

Edit: Also if its the last echo before unlocking the boss and you don’t want to do another echo it might also be worth filling out some extra stability, if its needed to unlock the boss