The 1970s brought us bell-bottom pants, leisure suits and the Designated Hitter. Two-thirds of those abominations are gone, thankfully. Too bad the DH is still with us. The DH has its supporters, but I think it's hard to endorse both the DH and interleague play at the same time.
American League lineups are built around the DH.
The flip side of that coin is arguably worse. In AL parks an NL team often moves a regular into the DH spot to "rest" him. A benchwarmer will take the regular's spot in the field and give the NL team a ninth bat, though not a potent one. It doesn't make economic sense for NL teams to pay for a quality hitter on their bench. Interleague play will put a few extra NL hitters on the fantasy radar. None of them, however, will come close to replicating the value of the American League DHs that fade during interleague contests.
The extra NL hitters with some fantasy appeal, even a little bit, are for better. The ones that have little to none are for worse. Some of them are far worse and no better than the pitchers that they replace in the order.