Currently the Marine repair time is in no comparison to the building heal time of the aliens.
I don't know exact numbers but it feels like you can weld a nearly destroyed CC in 20sec to full health while it takes several minutes to the same with your hive as a gorge.
The long healing time for hives allows marines to do a "attack the hive, die, run back to the hive and attack it again" tactic. Which is impossible for the aliens if there is one marine/MAC welding the CC.
I also think it should be taken into comparison that the marines have to spend 5 res and still stay a "normal" marine which can fight pretty well. The aliens have to spend 10 res and have to spend a bit time evolving to a pure support unit. If the gorge wants to return to combat after healing the hive he has to evolve to another lifeform which will result in losing at least 5 res in comparison to the marines.
The heal spray feels okay for healing a group of hydras, with normal buildings it could be a bit more. The healing value while healing players is fine in my eyes.