My brother is a Pure Malt FANATIC. He has amassed several full bottles and has a large box of wrapped official sample packs. There is a positively tremendous batch variation across the batches. He has full bottles of the first two batches (I could get batch codes, but not tonight. PM me if interested.) and he had me try them out. The first batch has a much sweeter boozy base and lasts way longer, while the second is far drier and almost woody. The first batch has a more distinct berry in the top notes as well, while the second is more believably whiskey. Surprisingly, he favors the second batch, although it lasts a couple of hours less than the original batch. Either way, they both last waaaaaaayyyyyyy longer on me than you mentioned, and fragrances don't usually last too well on me. Perhaps your fragrance is damaged in some way.
These are allegedly aged in used oak whiskey casks, which could easily explain the variation. Very cool! This is one instance where I think it's rather okay to have wild batch variations in perfume; that's part of the concept.