My Raven npc hunting setup:
High slots : 6 Named siege launchers. (I use arbalests, but theyre stupidly expensive, so you can use Malkuths or Limos), and 2 Heavy Nos, preferably named. If you use normal sieges thats ok, but you wont be able to use your other 2 high slots effectively as you run out of cpu. Also remember the type of torpedo you use depends on the rats you are killing.
Medium slots: 1 c5-l XL Shield booster, shield boost amp, cap recharger II, and 3 shield hardeners. (The type you fit depends on the rats youre killing, for example, guristas, fit 2 kinetic and 1 thermal).
Low Slots: 5 Power diagnostic II
For info on what damage rats give, and what resistances they have so you know what type of torp to use, go to:
http://www.eve-db.com/database/
and run a search.
This is a very expensive setup I know, but worth every penny! In this setup, I can take any lvl 4 mission easily on my own, and I even managed to clear the first 2 levels of the lvl 10 complex too.