No, I don't think so at all really - why should one person automatically get the perceived 'good' ones?
I think giving a variety of abilities to each pro means that we get to see more of their character and teaching ability.
To me, Brendon was lucky in his first partner - Natasha was a good dancer and also quite compliaint - but Sarah being a bit less of a good dancer and more fiesty showed a different side to him, as for Fiona - well best not get me started on that (what the heck is she still doing there - the girl can't dance - I know Julian couldn't last year but at least he tried!)
Again, last year Darren struck lucky with Jill, but I think we've seen more personality this year with Gloria.
Erin has put the spade work in, if you like with Martin Offiah and Julian Clary (both were pretty obviously not born to dance!) and this time has been given Colin who allows her to show another side to her teaching technique.
Anton, after the 'older' ladies of Lesley and Esther has been given a younger partner in Patsy
I think it adds to the programme - it would be boring if the same pro dancers just went through the same routines with the same character of celeb.