Quote from Kaleido_Galaxy
Do you still need help with this boss? If so, here's a strat a friend of mine gave me for solo'ing inferno Belial on her DH...
Got any increased attack speed rings and amulets you're not using currently for your max DPS set? Give them to your Scoundrel.
Give your Scoundrel any old ranged weapon with increased cold damage on it (very important). Favour hand crossbows or bows for faster attack speed.
Spec your scoundrel for increased damage on crits, triple shot, blind, and slow.
Your listed DPS stats are good so far. Here's what you do to improve them for this fight and for may other solo fights with monsters that can 1-shot you from now on...
Get a decent increased cold damage ranged weapon (700 listed DPS or higher) for yourself, unless you have a very high damage non-cold weapon. A socketed or in-house increase critical damage stat on your weapon helps a lot here.
Use the standard DPS spec:
Prep (Focused Mind)
MFD (Mortal Enemy)
Steady Aim -OR- Cull the Weak if you're using a cold damage weapon and your attack rate is faster than 1.5
Stand in the corner. Nuke.
Hungering arrow single mobs, Nether Tentacle groups.
Leave the last serpent guard alive. Let you Scoundrel and Bat kill it while you run around avoiding it to build your Sharpshooter to 100%.
Get in position so that when Belial comes down, you can just barely see him on the left side of your screen.
Mark him. Hit him with a good number of Nether Tentacles. Smoke Screen to avoid getting hit.
After his third attempt to melee you, he'll switch to ranged shots. Make sure you have a full tank of hatred and nuke him. Keep your discipline recharging using an early Prep and time your Smoke Screens to avoid getting hit by his ranged attacks.
If guards begin spawning, use your Smoke Screen to get them to line up either around, in front, or behind Belial such that your Tentacles take care of them while continue to also pumpel him.
Lastly, win. And let me know how it goes. I like feedback.
Edit: FYI, I've completed Inferno and killed almost every champion/elite monster I've come across using a 890 DPS cold damage bow with +70% crit damage jewel with the exact same spec I linked above. Just in case there are any objections to using a cold damage weapon
Offtopic, how did you manage to get over ACT III elite packs called Soul rippers I think, the one that hit you with their tongue?