I regularly dish out 300k+ damage, about 20k heals, and anywhere from 10-20k protection as a L50 Madnassin.
I use Dark Charge, not Lightning Charge, for PvP. Use a shield, not a Focus. This increases survivability quite a bit (especially with the Charge Mastery talent). This also allows me to guard a healer and tell him to watch my *** (which also nets more medals). I crit for over 3500 on Assassinate and about 3200 on Mauls. I start off a little slow, but once my target dips down to sub 50%, they're probably going down without a lot of heals and CC. The crit Maul/Assassinate combo will take nearly anyone out at that point except for tanks.
Death Field also crits for 2500+ to 3 targets. Meanwhile, I'm randomly dotting people up with Creeping Terror, and any procs I get for instant Crushing Darkness. Thrash/Shock until the target is low enough to burst, randomly taunt other enemies that are wailing on team-mates. If you're in a large battle, liberal use of Overload, and the AoE taunt will reduce a significant amount of damage (unless they get smart and try to focus you - then pop defensive CDs or try and Force Cloak out).
Recklessness if you can afford to throw a full Force Lightning at a critical health target, etc. Creeping Terror is also especially useful for kiting enemy melee - allowing your short-ranged attacks to whittle away their health until you get them into "execute" range and finish them off.
All of my gear is built for high willpower, crit, and surge. It's also excellent for PvE.
I've never lost a straight-up fight with a 50 Deception Sin (it's usually not even close, even with CDs down). I frequently kill players 1v2, 1v3, even a few 1v4. Hell, I had a game earlier today where I did 330k damage with 49 kills and Zero, yes, Zero Deaths.
Do you have a link to this build? I'm interested in checking it out.