Well ranged dps have to worry about getting his by aoes and hostile fire all the same. Really only the cleave puts melee at risk. Also something to take into consideration, ranged dps mostly take care of all the mechanics so melee can continue to dps. I.E. activating switches, tethers, landmines, kiting, towers, etc. This isn't exclusive, but 90% of the time, this is the case. On top of all that, dps melee has the highest dps in the game, so there is balance. You can complain about keeping up your rotations while keeping positions, but ranged have to keep up with rotations while moving all over the arena taking care of things so you can keep your GL stacks.