I don't think that they have focused too much on Hal, necessarily, in most episodes, but I do think that they are telling the story in third person, instead of through Malcolm's eyes.
I agree that the show has evolved, and there are some things that we can't return to and will never see again. Malcolm has sort of become the school creep; we saw him abandon the friends he did have (the Krelboynes) back in Humilithon, and with those characters now doing outside work (Kyle Sullivan, Dabney, has his own show this year) the chances that we'll ever see the Krelboynes again is quite slim.
The truly original storylines we had when Malcolm was a Krelboyne were fantastic. I would really like to see something like Krelboyne Picnic done with the Buseys, but through Malcolm's eyes, like the rest of the series has been, making at it a very unique epsidoe in that we're exploring a new and different side of Dewey and using the Krelboynes, seeing the humiliation in Dewey, but sensing it through the eyes of Malcolm.