The pack in question:
http://www.botachtactical.com/ebmcm3oppa.htmlGetting any recommendations based on any particular make and model is going to be hit or miss and is likely to be subject to a strong self-selection bias. Your talking about a $390, plus S&H, backpack marketed toward military, or wannabe military, users. There are just too many functionally equivalent backpacks out there for there to be many people who have bought that particular make and model. Those who have spent close to $400 on a backpack are highly unlikely to be anything but complimentary.
A guy who spends $60,000 on a sports car is unlikely to admit it isn't functionally any better than a $12,000 econo-box. Even if the former gets most of its road miles behind a tow truck, and spends more time in the shop than his garage, while the later is a guaranteed smooth, if not exceptionally high performance, 200,000 miles with above average fuel economy. But then again the econo-box comes with no bragging rights and the sport car looks good standing still.
You may see it differently but IMHO just about any full sized pack can carry a rifle sleeved and strapped to the side or back. It isn't hard to rig up and it isn't uncommon for people to see hunters packing their rifle without resort to a specially designed pack. Most packs built in the last fifteen years has provisions for carrying a bladder. Those that don't are usually not difficult to convert. Often just a matter of opening up and stopping a seam for the hose.
As far as similar sized quality bags go I suspect that you could get one for a lot less than $400. Catch a sale and you could save close to $200. It wouldn't have the nifty name, macho mystique of a "true go-to-war pack" or features designed for a sniper, and so it might not do it for you, but alternatives might be worth consideration.