Vortex doesn’t offer something in the size and magnification range OP asked about. The 3-18x50 is what, 44 ounces? Good scopes if weight is NO consideration.
I agree: the quality is excellent, and it’s hard to find a more expensive scope at a given magnification range than the NXS. Oh, there’s a few options from US Optics, Swarovski and Leica, not to mention the Nightforce ATACR series, but…
Anyway, it’s a premium product, the quality is there but it isn’t cheap.
The Mark 4 sold-as-such is discontinued, but the “new” VX3i-LRP line has some very familiar looking scopes:
https://www.leupold.com/hunting-shooting/scopes/vx-3i-lrp-riflescopes/
OP: I think the NXS is a better scope than the Mark 4 in most ways. I would consider a Mark 4 only if I could get a great closeout deal, which I did last year on one btw. At standard prices the NXS is an OK deal, and one of the best available options for moderate size with high quality and ruggedness, while the Mark 4 was overpriced. If it were my rifle I’d look at the NXS compact 2.5-10x32 and 2.5-10x42. I don’t like the pushbutton “digillum” on the x42, however. I hate single-pushbutton systems in general, and I think Nightforce’s implementation is among the worst, compared to say Leupold’s. The older x32 has a dial and doesn’t suffer from this problem.
Another option you might consider, although heavier, is the EOTech Vudu 2.5-10x42, which has outstanding illumination and overall seems like a very strong challenger to the NXS Compact 2.5-10x42, except for weight. EOTech uses a button system but has three of them, separate ones for on/off, brighter, and dimmer, and the reticle has no bleed or fuzziness issues - I’ve seen uneven illumination and minor light bleeding on several NXS scopes I’ve had my hands on, as well as a SHV (which appears to be derived from the NXS). The EOTech Vudu has perfect, even illumination that previously I had only seen on Steiner Military scopes. The Vudu scopes are made in Japan by LOW and I would assume they are no more likely to have temperature sensitivity issues than any other premium scope made at LOW, which includes the Nightforce NXS and SHV series, and major components of all other NF scopes.