Narcs wont hit mechs moving sideways. Almost every mech moving at its top speed will be to fast for the poor narc missile.
Shoot the narc if the target is either stationary, or not running sideways.
There is no inherent property of the NARC to miss every moving Mech. Learn to lead your target
. It's just very hard to do, but it can still be achieved.
On the subject of other NARC musings: recently I had a game, where the fired NARC simply immediately vanished, if I had a lock on a target. I hear the firing sound and everything, I was not hitting myself or anything else, but the NARC simply immediately vanished. As soon as I removed the lock, the NARC fired normally.