I think we have enough discussion on Berggren to understand why he sent and keeps sending him back to the AHL.
Edvinsson was a weird situation because there was no way to be positive whether or not he would be healthy and clear of rust to start the season after entering the offseason with an injury. We signed vet filler depth that is inflexible, while Edvinsson's contract has a lot of flexibility. Not hard to see why he was sent down to start the year.
Kasper probably could stand to play more in the AHL, but it depends how they approach the offseason. Like do you bring Perron back to play on the wing, or do you leave that spot open. It is one thing to sign players to force a single, young A-tier prospect or typical B-tier prospect to be better than the warm body vets. In the Wings position, you have Berggren, Kasper, Danielson, and Mazur all in the system and close to making the jump. The competition and the "earning" it aspect is going to be competing with their teammates for the last spot. I don't need to see all of Fischer, Perron, Sprong, Czarnik, Kane brought back. Pick the couple that you think are legitimate assets to your team and bring them back and then let the prospects fight amongst themselves for the chance to be up.