As it stands right now, there's no situation in PVE where these two classes of weapon are the best option available. Sure, you can use them as a preference, but you'll be less effective than someone using a rocket launcher, sword or Merciless. The only situation I can think of where a case for using a sniper can be made is Calus. And even then it's pretty debatable whether you'd be better off slotting something else. Honestly, I think it was a terrible mistake to take these guns out of the middle slot.