Nightforce lists the 12-42 nxs as having 45 moa adj. range. My loads won't get me to 1500 yards with that. What ranges are you shooting now, and what scope are you using?
This is your issue with the 12-42 NXS...you just don't get the elevation to dial.
I personally feel that right now, the Bushnell XRS with a 4.5-30 and FFP for hold over in your choice of reticle is pretty hard to beat. It's what I'll be ordering up here soon with an H59.
The March optics are awesome for big zoom, but you're looking at a big price tag as well and still get short changed with elevation adjustments.
Most of the high zoom optics are designed for the bench guys and don't need the elevation the ELR shooters need...which is where the hold over comes into play.
You could get a 30-40 MOA rail but that depending on your barrel length, you might start to see in your FOV.
Do the math.
The XRS comes with around 28 Mils of internal adjustment lets say you can use all of them if you pick up a 20 MOA rail, (that's probably wishful thinking but you could always get a 40 MOA rail) and anywhere from 0-30 mils of hold over possible...depending on what you're zoomed in to. On Max power, you can hold somewhere between 6-8 mils pretty easy. Same with the G2 reticle.
SO, you essentially have somewhere between 32-36 mils to get you as far as you need to go. Somewhere around 120 MOA on full power.
Back your optic down to 25x or 20x and you'll have TONS of elevation to hold.
That's a long way out der!