The piece isn't even BiS for anything for ranger if I'm not mistaken. Just level and gear up COR and don't worry about ranger.
In comparison to Orion +3, Nisroch is:
-15 racc
-1 STP
+10 Crit rate
+5 True shot
If able to utilize the True Shot, there is absolutely no contest. If not, then it's a bit closer, but it's going to be very hard for 1 STP to beat 10 crit rate. The piece benefits COR a good amount more than RNG, as COR's only other reliable option is Mummu +2, but it's still good for RNG, too.
As for the OP. If trolling, meh. If not, precast set incorporates Snapshot and Rapid Shot, midcast set is your racc/ratk/STP/crit stuff. The guide is outdated, but read through the Preshot, Midshot, and Utility threads for good gearing advice.