Hazard Emitters is the best hull heal in the game hands down. No engineering power comes close. (maybe miracle worker but you gotta be an Engineer Captain for that) I run two copies on all my science ships. You can chain them together and they also grant a hefty damage resistance as well.
Engineering Boffs are much better used for shield healing powers like EPtS and RSP.
Run two copies of HE, 2 copies of TSS and a Science Team. Use your Engineer for EPtS1 and RSP1 or EPtS2. Now you are an uber healer. Instant heals like engineering team and aux2sif are useless because they are so weak. Enemy focus fire will still cut your allied ships to pieces. You need sustained healing and damage resist from HE in order to save them.