I feel like the lack of the "war zone" feel is actually due to large size of the levels and the lack of singular focus points during matches. If you look at Battlefield, the times when that game feels most intense isn't on the massive maps, it's modes like Rush when you have a bunch of players all fighting over a small section of a larger map.
The bosses in Warzone were obviously an attempt to get players to bunch together and engage in combat but I feel it didn't really work. The bosses aren't really fun to fight and making the last shot be the only one which counts means that people aren't that excited about fighting them. For the next iteration I think they need to add more compelling objectives to draw players into certain areas of the map. Stuff like capturing a point somewhere awards you some points and gives you a rare tank.
I also think the opening of Warzone matches sucks. Whoever thought the best way to start a match was kill some really easy AI then either sit around capturing an armoury or run across half the map to find the enemy was completely wrong. I think each team should spawn on either side of the main objective, that way the start of each match will be an epic 12v12 battle over who gets control of the center. Far more exciting than killing a few Crawlers then sprinting for a minute or two. Each team should also start the game with control of one of the armouries.
Pretty accurate stuff here.
I think the biggest issue is they have these massive maps, meant for people to navigate creatively, but the primary scoring device (capturing base) encourages people to stay put. As a result you often have these vast areas of emptiness that are only populated when key enemies spawn in them.
To fix this they need to remove bases as a scoring device. Instead point should be scored for Spartan kills, boss kills, and randomly generated objectives (like CTF and planting bombs). There should be atleast one live objective at all times.
Bases should be used to open certain types of Reqs for use, and should be map specific. Map A could have an Armory, a Garage, and a Hanger - and capturing these point would unlock Heavy weapons, ground vehicles and air vehicles respectively (For Example)- so there'd be a strategic element to capturing bases- but it would be the end all be all.
Rather than have a triple cap open the opponents core, I'd just have hard to access switches that make the opponents base vulnerable at anytime.
Also, bulletsponge bosses are corny. Instead boss fights should be Leaders who must be killed in specific ways who are flanked by a ton of normal strengthed enemies. Say, a speedy Elite who must be backsmacked. Or Bashee Pilot who must be boarded. The challenge would be dispatching their cohorts and enemy Spartans so that you can get in position to seal the deal.