I find the cooldown more useful. When one of your Sunspots gets popped or when your team are spread out somewhat it’s easier to just put another Sunspot down. I also find it more useful when your team are moving from location to location. Your team don’t need to run back to a Sunspot if you can cast another. When the Sunspots are on a short cooldown I like to keep one by my team and use another to harass the other team.
I can see if you wish to fuel the Sunspots with Ambra’s mutation the extra health could be useful but I’d personally rather be keeping my eye on the other team rather than my Sunspot.
I do sometimes find myself wishing for the extra health sunspots but if I need to keep healing I can use the staff to heal team mates in between.
I would expect playing the Sunspot feeding Ambra would work really well with Kleese. You could build a small fort and get someone like Ghalt to drag people into a world of pain.