Have the people arguing that it is too strong ever actually seen a generator blow? Like one that is under full load, they can go with a huge bang, 10x more sparks than this reworked one, with lots of fire. I am going to take an educated guess and say no, they have not seen one blow.
If they hide the box a bit. I don't mind the change, it is still in keeping with what a real generator going bang looks like, the effect was missed by many people, so ramp it up a bit and let it go with a spectacular bang. There is nothing subtle about that scene, dark forces come and make themselves present in quite a dramatic way. It is still in keeping with that scene in that sense. If the reason the generator blew in the first place is because of the dark forces visiting, (pretty sure it is) then I would argue that the previous sparks were actually a bit too subtle, as it conveys a sense that things are under control. They clearly are not. Having larger sparks will help convey this quite well I think, as things go from normal to bad quite dramatically and quickly, with or without the sparks.
I also think they should perhaps install a single electric blue strobe light next to the generator, hidden from view that flashes a couple of times up the wall behind the generator at the same time the sparks trigger, to give the sense of the electricity actually shorting and arcing. When generators go bang, they do so with normal sparks and usually a few bright blue flashes from the electricity.
I would argue that this ramped up effect is actually quite subtle to what can happen when a generator blows. I like it.
