Dyson certainly had value to that team, but this misses a very important point, which is that Stan was in Calhoun's doghouse pretty bad that year. He was getting limited minutes (2 against L'Ville as I recall), and was getting yanked at the drop of a hat when he screwed up. After Dyson went down, Calhoun had no choice, and Stan started getting huge minutes, with no fear of getting pulled . . . and in the games Dyson was out, Stan played some of the best basketball of his career at UConn. In the final four loss to MSU, he went 4 of 5 from 2, 1 of 1 from 3, 4 for 4 from the line, for 15 points, had 13 boards, and two blocks. He was all over the place, and that was in 31 minutes.
So, while it's fair to say that Dyson going down was a loss to UConn, the net was nowhere near as bad as lore has it - a large chunk of his minutes went to Stan.