If you're characters are low levelled then go level them up first cause otherwise it'll just lead to more frustration...
I had a bit of trouble with these guys too cause they kept giving me ailments... but the way I did it was to make sure I was stocked up with loads of smelling salts, alarm clocks etc... and then I just targeted them one by one... I think they don't have that much HP anyway so if you level up your characters and get some good weapons you can take 'em out easy that way.