It is actually a counter-sniper rifle... intended to arm each platoon with someone easier to train than a sniper but more effective than just some guy spraying with an RPK. The rifle was intended for designated marksmen.
As to overheating, ALL rifles overheat. Period. My M-14 has a heavy National Match barrel on it and if you shoot it at the same distance you notice that it shoots higher the more you shoot it. It is the nature of a firearm.
I trust that the PSL can hit a man sized target to 800m, which is what it was intended to do.