To many tubers? no such thing. You just have to start trading them away for others. I don't know how long you have been growing dahlias, but some of them make lots of tubers, and some make very few, it is just part of their genetic make up. Also some make tubers that store easily, some make tubers that are prone to rotting. One of the things you can count on when buying from Swan Island is that you will have good tuber makers that store easily - they stay away from the more difficult ones.
Dahlias do need more fertilizer than perennials. After all they do a lot of growing in a single season. I just basically treat them like I treat my vegetable garden.
And yes - some of them are just so gorgeous that I can be happy even if I don't get many blooms. Might be different if I had only 5 or 6, but with so many in my beds, if a few are stingier with their blooms I can live with it.
