I'm opposed to Dry skin as i think its Fire STAB will be much jeopardized: nobody will use it under sun, which squanders the 1.5 bonus of its Fire-moves, while in rain, well i agree Fire is still useful for detering Ferrothorn, but still this means being walled by Jirachi, Bronzong, and even to a certain extent Gengar! All of which are not designed to be counters/checks in the first place. Defensively speaking Dry skin is just a means of getting rid of the stealth rock weakness, which is another way of sneaking around the typing instead of using it. therefore this poke will be used in spite of its Fire-type, which is exactly what we want to avoid.
That is why i advocate Water absorb, over the others abilities because i feel gaining hp back is a much better way of checking Water-types than getting a spAtk boost, because of the stealth rock weakness.
Changing weather is for me an ability that will deter cap 3 too much of its original purpose.