sinx: I think you'll level faster with grim than with DD, you can still keep your build but use a katar to grimtooth. At 7x if you have someone to help you could try Rachel 1, if that's too hard, try killing soils.
snipers: Thor 1. You'll think I'm crazy but give it a try, with traps and by being very careful you'll kill monsters that give you insane exp at your level. Fly wing away at the sight of guardians, stay away from salamander. Kill imp and kasa only. If you find it too hard go to level 2.
pally: GC in niflheim or geffen 3. If you're not GC build no idea, never played a crusader actually.
Alch: not really good with that class, do you have a homun and if so which type? Melee alch level the same place a smith would I guess.