They're supposed to be a wake-up-call. If your character can't face them, though, you're going to be screwed once you get to Golgotha, trust me -- it only gets harder from there. You need to rethink your character build, basically.
Try to focus on one or more of the following:
1. An escape option that guarantees at least short term safety. The Teleport or Phasing mutations are good for this. When you see something dangerous like a Slugsnout, get away immediately.
2. A way of killing or incapacitating dangerous enemies very quickly. Charge or a powerful ranged attack is essential for non-mutants (and doesn't hurt for mutants, either), but obviously if you're relying on charge you also need to be deadly at close range. For mutants, Sunder Mind or one of the AOE blast mutations works; so do the stinger mutations, the hand blasts, etc.
3. High HP. Try not to make characters with less than 18 toughness unless you're really sure you know what you're doing (and have a lot of other stuff from this list to cover you.) A level ~7 character who isn't insanely focused in one area ought to have enough HP to tank at least a few hits from slugsnouts; if you're insanely focused in one area and are dumping toughness, your area of focus needs to be powerful enough to kill enemies like that quickly.
4. Very high dodge. This is much, much less reliable than the other options, but it does help against Slugsnouts.
5. Early ways of detecting enemies. Clairvoyance, domination, sharp hearing (you'll have to level it up for it to give you enough warning, but it's worth it), etc. With Clairvoyance + Sunder Mind you can even kill enemies before they know you're there (but again, if you rely too heavily on this Golgotha will eat you alive.)
6. Allies. Use Proselytize, Beguiling, or Burgeoning to get people who will soak damage for you.
I was playing a character earlier with Fragile Bones, Teleportation, Phasing, and Electrical Generation (remember, Fragile Bones meant that slugsnouts would do +50% damage to me!); but they weren't a problem. When I ran into a dangerous enemy like that, I'd phase in close to them, hit them with my stored Electrical Generation, then teleport to safety if that doesn't work. Another variation uses Poison Stinger instead (hit and run until they die of poisoning, naturally, though unlike Electrical Generation you can't use your stinger while phased.)
What sort of builds are you using? What sort of character are you trying to play? I can give more specific advice if I know that.