first thing to note, the gameplay in the division is not your typical fps like say counter strike.

it may take multiple headshots to kill someone for example (exception being PVE content which sniper shots to the head seem very effective versus pvp). also there is a health point spongy effect, meaning players can unrealistically take a huge amount of pummeling from bullets without dying, IF they are speced with enough health points, stamina, armor, and other abilities that heal and boost dmg reduction. so fps purists that prefer something more realistic may not like that. just think of the division as a fps rpg hybrid.

the most crucial part in this game other than your point shoot kill, is you farm gear loot (weapons, armor, accessories,aesthetic skins, currency,crafting materials, keys to open chests for loot), unlock abilities/perks ...... think of it like the diablo of fps meaning gearing out your character to improve them is part of the fun besides just killing. so then my AK47 may be way better than yours.... due to my gear/abilities loadout which is superior and plays uniquely different than yours.

the PVE aspect of the game is basically doing main missions, side missions and events. also roaming around the game map to find hidden areas, treasure in obscure corners etc. point being to level up, farm stuff, unlock things etc....

the end content will be the competitive aspect of the game which lies in the darkzone. This is not like counter strike 5 vs 5 so pvp is already started right of the bat with enemies already clarified. no, everyone in the darkzone is a POSSIBLE threat to you. the pvp is player driven, meaning it's up to the player to decide to attack you out of the blue. So if nothing is forcing people to go rogue, then won't the pvp be dead? well certainly if everyone in the game was a carebear sure, pvp would be non existent. However there are many good rewards for going rogue such as stealing loot, fast dz exp leveling. however there are huge risks that you lose 3 times more when you die such as dz keys, dz exp, dz credits, the loot you carry in dz stash (not your equipped gear of course, or your stash stuff outside the dz or in your normal bag inventory space).

to be more accurate, the DZ is also a PVEPVP hybrid. so to fill in the time gap when there no rogue action taking place, players can simple farm the ai to farm dk keys to then loot chests using those keys to then extract the loot back to home base stash. once the gear is evac/extracted, you won't lose it after dying in the dz. in fact you go back to home base to access your stash to equip or sell the gear your found.
Also it's important to note they said DZ is not the only endgame content. there is rumors there may be raids involving at least a group of 8 players to do it. Is this true? i don't know but what else could it be?
content wise, it's been compared to fallout4 in being similar in map size. dark zone are is 1/3 the size of the total map and will be split into 6 dz zones for different dz level ranges of players. my guess this means once you hit a certain dz rank, you progress to the next dz area with higher dz lv range for example. so the remaining 2/3 will be the pure pve areas of the game.





https://division.zone/2016/01/16/tom-clancy...-size-revealed/
bottomline, is this game realistic, somewhat, but the mechanics such as spongy hp, effects/abilities make things obviously unreal. But considering it's ton of fun i don't think it really matters. though some reviewers like totalbiscuit were a bit offput by it, but i think their missing the point that the division despite being a tom clancy isn't about going full on realism, but to make the fun factor by combining fps with mmorpg. and yet they stubbornly expect this game to follow fps purist rules since anything else is sacrilege. but to each their own 

you can view his review here (though i don't agree with some of what he said, but you decide for yourself)

by the way i'll be focusing on a high stamina + armor build using assault rifles and possibly even a sniper rifle.