What about giving power nodes a boost to health based on how many structures they are powering?
By default, they'd have the same 2000 Health/1000 Armour.
With every additional structure they'd get X health/Armour, which could be based on the cost of the structure.
That is, an increase of 100 Health/50 armour for every 10 res the structure costs.
That'd give them a boost of 100h/50a for an Armoury/Extractor, 150h/75a for an Observatory/Infantry Portal/Phase Gate/Robotics Lab, 400h/200a for a Prototpe lab, 250h/125a for an Arms Lab.
Assuming you had two IPs, one Obs, one PG, one Prototype Lab, one Arms Lab, an Armoury, an Extractor and a Robotics lab, the health boost would be 1350 Health/675 Armour.
The total would be 3350 Health/1675 Armour.
That would be a total of 6700 effective damage it would take to kill one, as opposed to the default of 4000.
The health bonus could be adjusted for balance reasons.
I honestly think 200 Health/100 Armour for every 10 res would be better, but it's better to start low and then increase.
I prefer to buff things, rather than nerf things, and I think this would prove to be a substantial buff to Power Nodes if implemented.
A similar buff could apply to cysts.
Give cysts near structures more Health/Armour.
100h/50a for every 10 res, at a cost of 1 res would be a 10h/5a boost for every nearby cyst.
Most cysts in hallways have tend to have max of 2(More in hive rooms/important locations) neighboring cysts.
So the bonus would be 20 Health/10 Armour on average.