Well from what I have heard about making Saison, you want to use higher ferment temps. We are talking up to 85 degrees. So what I would do if I were you is ramp up your ferment temp to 80 or above, a couple of degrees at a time, so that you are at 80 or above by the end of the week.
Now as to WLP 568 being a bad strain for saison, I have never used it but from what i read on the white labs site and what i have heard about saison fermentation from the Jamil show on saison, that the white labs saison 2 and saison blend (which you are using) were just created to address a problem that was typically encountered with their original saison yeast, where fermentation would stick about 3/4ths of the way through. So these 2 strains were developed to be easier to reach full attenuation without having to resort to pitching a second yeast strain or anything like that.
But don't take my word for it, I highly recommend that you listen to the jamil show episode on saison, it is an excellent show, and Chris White from white labs comes in and discusses many of these saison yeast issues. I found it extremely informative.
Heres the link if you don't know about the jamil show
the saison show is 9/10/07