The Nikon Venturer LX is a top of the line binocular, I believe them to be in the same class as the Swarovski and Leica glass. But why does Nikon not make them water proof?
My dad use to use a Tasco scope on his Browning 30-06. Then one morning on a late Nov. Elk hunt, he pulled up to shoot a nice 6x6 bull and found that his scope was fogged and the crosshairs were gone! Needless to say, he didn't fill his tag that year, and our family stays away from Tasco.
Hmm, the Venturer LXs are waterproof...nitrogen purged and all that. Is it possible you are thinking of the Nikon Superior Es? Or E2s? Both of those models are not waterproof and are thought of very highly for the image they provide. To answer that question I would say that both of those models are of the porro prism design and it is typically difficult to waterproof them considering the style of focusing mechanism.
As for the Tasco, don't put too much stock in my commenting on them. I am not as much a rifle hunter as I am a bowhunter. My rifle, a 40 year old Remington 336C chambered for the 35 Remington cartridge, really only gets taken out of the case 5 times a year. Twice to practice before the season and usually only on our opening day and the two subsequent Saturdays. Work and the short length of our rifle season prohibits its use more than that. I have had that Pronghorn on that particular rifle for about 6 years now. No problems whatsoever. But when you consider the caliber and the limited amount of usage then you can probably see what it continues to stand up so well.