Healing in PVE
All stats in gw2 are linear. Regarding linearity in percentage, every stat will go into saturation by increasing it. So if 1000 healing power are worth it, then 300 are all the more.
The question you should ask is not if so less HP is worth it, but if HP at all is worth it.
And the answer is difficult. HP is not worth it if….
… u do speed runs
… u love CoF or CoE or other dungons which are used to get done in speed runs by PUGS
… if you do no damage because of healing build /equipment
… if you don’t have multiple sources of group healing
In my opinion, engineer is one of the best – if not the best – party healer. But I would never go for healing equipment except celestial gear which ensure you also good damage and surviveability for agressive acting with bombs.