Yes, the water profile is important as it will have an influence on the finished product but one cannot say "Use this profile for that beer" unless he knows what the brewers criterion of optimality is. The obvious one is to make an 'authentic', in this case, Saison. To do so one would want to use water typical of the water used by Saison brewers and to treat it in the same way they do, or did (does authentic mean like the ones being produced today or in yesteryear?).
Another optimality criterion is the best tasting beer and the immediately following question is "according to whom?". I well remember sitting at an investor's meeting at which the guy sitting next to me commented "This sure doesn't taste like any Saison I've ever had but it sells like hotcakes so I don't care." "Whom", in this case, was obviously the customers. Another possible "whom" would be the judges at GABF or, in the case of the home brewer, the judges at the competitions he enters, his spouse and friends and ultimately, himself. Accordingly, the brewer must experiment. I usually recommend starting with nothing but RO water to which a modest amount of calcium chloride has been added. This gives a basic foundation of some calcium paired with chloride which is almost always a benefit and thus nearly always produces a good beer. Stepping off from that point one quickly (time measured in units of brews so it can actually be a long time if one doesn't brew often) determines whether some sulfate should be added to the chloride or replace the chloride etc.
