I always thought explosions should be like this...
Example: Lets say...Goku shoots a Kame at someone, it misses, and hits the ground. Now, instead of the explosion being a 3-D sphere type thing, I think it should be a 2-D Ball that always faces you, and expands when it strikes as normal(the blast would look sort of like the charged kame, or spirit bomb or something) I think this would make things look much more 'real' and it could add the TV show effect of the explosion as a screen, and you dont quite know if your target is dead on the other side.
As for dust, I had an idea for that too. Along with this 2-D ball of light, as it hit the ground it would make little 2-d sprites of dust kick up along the contours of the ground its on(it wouldnt do anything in the air, obviously. I made a little diagram to explain...
Goku would be the red circle. See, on the ground, the blast would make dust just fly out at its edges. On the hillside, it would follow the contour. Get it?