I totally hear all of you on the performance and reorganization woes here. Although this opens another can of worms— We recommend that you keep dashboards to under 25 tiles due to performance concerns like the ones you’re talking about. As @Dawid_Nawrot noted, performance issues are not necessarily due to the size of a tile or data itself, rather just the presence of a tile/tiles.
I was going to show a gif, but I don’t think I’m allowed because it’s still top-secret— We’re rebuilding dashboards entirely from the ground up and aside from Looking really pretty, the dragging/reorganizing chaos is gone, and performance is drastically improved at 25+ tiles.
Look for new dashboards coming to a beta feature near you in not too much longer. In the meantime, thanks for your patience (and thanks @Afroditi_Atmatsidou for the speed tip).