I've used the White Labs version, once. By mismanaging my temperature controller, my fermentation temp got just over 100F. In 4 days, my saison went from 1.060 to 1.010, but it didn't get lower after another month in the 70s. Sounds like a disaster, but it really didn't taste bad. Everyone says this yeast likes heat, so it may be that you really should have let your temp get higher than you did (but maybe not 100F!). This beer is a distant memory, though and I can't recall if it had grapefruit flavors. Even if it hasn't attenuated as low as typical style examples, the grapefruit part doesn't sound bad to me.