With all due respect then, allow me to address your post head on, in a non-confrontational matter. I agree with you wholeheartedly that merc dps right now is on the bottom of the totem pole. Why? Because of a few factors.
1) Mobility: While mercs are considered a 'turret' class like their brethren, the sniper, they have NO WHERE near as much mobility as a sniper does. Comparing turret tree to turret tree, Arsenal merc lacks the tools it needs to do damage on the move. Their rotation currently is frontloaded into Unload, which is extremely easy to shutdown, whereas snipers have an even spread of damage amongst all abilities. Series of shots was LoS'd? No problem, snipe/followthrough, which then sets up for a quicker ambush/followthrough. Mercs lack of mobility should be remedied by defensive cooldowns, which they lack as well, which puts me to point 2...
2)DCDs: If you compare a merc to a sniper, they're like night and day. The largest buff to snipers that people seem to FORGET is the Unshakeable buff they get from their cover mechanic. This is a buff that a merc, in my opinion, NEEDS to be even close to as effective as a sniper. This is why mercs fail alot, not only do they share the problem of LoS with snipers, but they also have their own problem in which they can be interrupted on almost everything, bar the Energy Shield talent in the healing tree.
Moving on from the unshakeable buff, as a sniper, in a 1 vs 1 duel with any melee, you stand a good chance at winning, with good rotations from cover pulse > running to 30m distance, Leg Shot > running to 30m, Debilitate > running to 30m, Flashbang > run to 30m, Covered Escape > Leg shot > run to 30m...You see where i'm going with this right? Snipers have an indefinite amount of utilities to evade melee's, Mercs don't have even close to that amount of utility and survivablity, which is their ultimate demise.
A dead dps does No dps.