I was able to work out the strategy for the rollers somewhat quickly (looping them around the pillar), however, their status as bullet sponges does mean there’s plenty of opportunities for things to go badly in the process (so, y’know, having to redo that fight in order to have an attempt at the content after it was a pain in the backside).
Re the ending and ‘three empty rooms’ - well, there is the question of whether or not the three rooms prior to the ending area actually served any purpose. Perhaps placing a checkpoint there, and building up some anticipation for A Big Fight may have been a better purpose for it (rather than fodder enemies), and probably would have worked suitably well given, y’know, SBIGJam and all that.
And honestly, I get where you’re coming from, about playtesting being a pain.