First off, I used to play 2 Abaddons for dps in missions (I was doing CPF, caldari missions) and had them both beam. I tried 1 pulse 1 beam and found that the BS's liked to hover outside good pulse damage range. I also recommend faction crystals, as T2 die too damn quick. If I were to go back to missions with not much isk to spend I'd do 2 Abaddons and 2 Guardians again easy. Ravens are doable (again cruise for range means less damage, but good projection) with basilisk support. If you have the cash I highly recommend Nightmares for DPS.

Abaddons are very common in nullsec doctrines at the moment, as are navy apocs, so going lasers/amarr is never bad (for future planning). Missiles are bad for anything beyond small gang PVP, and if larger scale PVP is a potential goal for you later then skip them. The only rats that I had problems with using laser dps was I think Guristas, and just skip those.

If you want me to tell you a path to make your life easier this is it: 2 Abaddons w. tech 2 lasers (both pulse and beam) and tech 2 tank and tech 2 drones, 2 Guardians with tech 2 tank and tech 2 drones, 1 Loki pilot (for frig killing in missions) with tech 2 everything, and a jack of all trades Noctis/Freighter/Jump Freighter/Indy guy. Upgrade your Abaddons to Nightmares when you get the isk and put T2 Tachyons on them and you will chew through level 4's like there is no tomorrow. Buffer/Resist tank everything, feed the battleships cap and armor reps and throw 1 armor rep/1 cap to each Guardian at the start and throw 1 rep from each on the Loki and you can ignore the Guardians after that on most missions (orbit them around 1 BS with an afterburner running and a buffer tank on them).