I've got a little Atom and it has worked well for me over the years.
I just use it as an 'add on' to my window cleaning, I only do bungalows these days as I don't have the time (or inclination) anymore.
I think the development of tools should not be focused on 'sucking', but more focused on getting underneath the debris to loosen it, (probably while the vac is turned off) so it can then be lifted out under suction.
It would like to think that it would be fairly easy to design a range of profile tools (for each shape of guttering) that can cut underneath to loosen growth. A tool to cut away the growth that has extended under a roof tile.
A range of tools to fit exactly into downpipes, that can create a vacuum to help lift debris and growth.
Failing that...a good set of double ladders.