The fact is Mercs were never "Overpowered". They should have not been nerfed to begin with. They used to be balanced as a ranged DPS class. Yes, prior to patch 1.2 you could simply spam one button (Tracer Missile) and do decent damage, but you would NOT achieve maximum damage by doing this. A lot of bad players decided to cry, cry, and then cry some more about this, rather than simply use their interrupts to shut "tracer missile only" mercenary's down.
Patch 1.2 DESTROYED the viability of the Arsenal Mercenary tree. It's as simple as that, and no screenshot of one or two mercenary's doing "good" damage changes that. Those same players would simply be doing even MORE damage playing marksmanship sniper, so its a moot point.
A class or tree is not fine when the role it is supposed to serve (in this case, "glass canon") is completely overshadowed by another tree/class. Again, Arsenal Mercenary is completely overshadowed by marksmanship sniper. The fact that mercenary has been left in its current state so long is just embarrassing.
It really is embarrassing. It's almost as if BW has no idea how to fix the merc and the sad thing is it's really simple. Make mercs more mobile by what i have proposed above. If not, give us back the old tracer missile or buff our damaging abilities by at least 10-15% so that we can at least compete in WZs.