Juggler as a 1-ranker sounds ok, but at 50% it should be advanced, IMO. I'm not sure by weans of what.
Besides I would just like to know why do you think it won't be overpowered to have a huge damage melee and a normal ranged at the same time? Poor demons ;) .
First off: discluding the LS, melee isn't quite overpowered. Most players consider it overpowered based on the AoB advantages and on the said LS, but with those off the table you'll be taking enough damage and dealing enough less for the game to be, possibly miserably, balanced.
Now, considering base statistics, the chances of a melee opportunity are rather small - 8 adjacent spaces vs. ~140 (I think) in-LOS non-adjacent spaces. Naturally, adding player engineering to the equation, the number of melee opportunities can become much higher, but chances can't be "often" without altering your location (or your targets), which often means walking towards your firing enemy. Massacre Man can reduce this process by one turn, which is fair. In those cases where a monster walks all the way up to you as you fire, it will certainly put you in a good position to retaliate, something which advanced traits are supposed to do - but consider that a good player will usually not let monsters that close, making strong monsters who survive so many shots (including Arach swarms in their caves) fair game. A player to whom monsters always catch up due to his skill won't be turning things around only thanks to this trait. Remember that the CS will be taking up the alternate weapon slot, making weapon swapping harder to control, likely killing off unskilled players more often than it will unjustly save them.
Back to the RL case, during those intermediate turns you could, instead of walking towards your target, swap to a CG/SG on one turn and begin firing it on your next. This means that there are already good options at the player's disposal. The Massacre Man trait will only be adding one to the lot, one with its own considerations, advantages and disadvantages. The cases where you walk back to fire your RL don't make sense, in context because they don't involve the CS in their considerations, and otherwise because walking back usually doesn't save you - your target will either fire at you or give chase, either way making swapping to a CG/SG more worthwhile, and anyway making this a judgement call with no obvious advantages, which is by definition not overpowered.
http://en.wikipedia.org/wiki/Baron_of_Hell#Baron_of_HellIt's said there once that they fire energy and once plasma, but never acid.
If that's not enough, I'll try to find a better source, which I know I have somewhere on my computer. Somewhere...
Just because the balls are green, doesn't make them acid. For one example, Fallout has green shots fired from the plasma rifle, and the colour of radioactive waste there is green. On a more severe note, most acids on earth aren't green :)
If the trait will be implemented, "Bloody Hell!" sounds great to me.