Use stormcaller or nova bomb for PvP. Trials basically shuts down sunsinger too, so don't use fireborn on it unless you plan on raiding. Which you will. Nevertheless, there are some quality shotguns still around, like the Chaperone. See if you can get your hands on one if you can't snipe. The last word is still godly and I recommend highly that you use it. But for PvE, Sunsinger and a pulse will do you just fine. Maybe the Smite of Merain if you can get your hands on it. Just run the raid a couple of times, transfer your highest light equipment to your warlock (weapons and shell, leave armor alone unless you're going to infuse into warlock armor) and you'll be just fine. Iron banner is coming soon, so prepare thyself guardian.