I've seen a lot of comparisons to Diablo, actually, too many to really make a list and as an on and off again Diablo player the loot system itself feels really close.
There is also a massive difference in TTK between certain types of enemies.
Red bar enemies are your normal everyday mob spawn.
Purple bar enemies are a superior spawn and generally have armor/do more damage/are more aggressive.
Gold bar enemies are elites and have the highest TTK while also generally being the most aggressive and damaging. A gold flamethrower boss is a royal PITA in a close quarters fight.
If you're geared properly, most reds die within seconds (as in I can drop 2-3 of them with a single mag from my rifle, which is on par for my level). Purples take a mag or two to drop and the best practice is to aim for the head where you're going to have the most crit damage/damage overall to drop their armor ASAP. Once their armor is gone their health drops in line with red enemies. Gold's that are the same level are a bit harder to work over than reds.
Cleaners are the only enemies with easily identified weak spots. Their flamethrower mobs will die from you puncturing their main tanks and causing an explosion. Boss mob cleaners have 2-3 tanks and hitting/destroying these will take good chunks out of their armor. The same goes for any grenade mob, who you shoot in the head as their grenade is charging to make them drop it. The same also applies to any mob with a weapon or wrench icon next to their health bar. They are carrying backpacks that will explode if triggered. In normal red mobs this will kill them instantly. With armored purple mobs this will nearly destroy them. With gold mobs this will take massive chunks out of, if not completely destroy, their armor. Of course, an elite boss takes more time than a standard elite.
I feel that if The Division had a more cartoony cell-shading style visual ala Borderlands or had you fighting magic monsters with magic/sword/arrows people (Most notably a lot of the earlier repliers to this thread) would be more accepting of the TTK and style of gameplay. It's an RPG first, a shooter second and the shooter mechanics are incredibly solid.
As far as loot types go, there are only a handful of types.
Primary: Assault Rifles/SMGs/Marksman Rifles
-ACR
-M4
-AK47
-Scar-L or Mk16
-Scar-H or Mk17
-FN FAL
-Vector SMG
-Aug SMG (Not sure why they called it an SMG and not just an assault rifle or if they really mean the 9mm variant that the aussie's have)
-Mp5
-M1A
-M44
-M14
-M60
-M249
-L86A2 LSW (LMG version of Brit Assault Rifle)
-Benelli M4 (Semi-auto shotgun)
-M870
All of these weapons can be equipped in a primary or secondary weapon position. All have some type of variation, whether it's a police model, military model, classic model or vanilla, etc. I'm sure there are more weapons but I cannot think of them off of the top of my head.
Sidearms: Pistols/Sawed off shotguns
-Beretta M9
-CZ75
-Sawed off Shotguns
-PF45 (?)
I'm not as up to speed on the sidearms. I've only used 2-3 so far in the game but they can also have military/classic/police designations, even if they don't really mean anything.
Outside of that list, gear comes in 5 levels. Grey (Common), Green (Uncommon), Blue (Rare), Purple (Epic) and Gold (Legendary). Once you've passed about level 10 the common loot pretty much stops dropping and everything becomes uncommon or rare. Purple's can drop from some bosses but are normally bought from vendors (right now) and will drop in high level areas. Golds drop from end game content (much like Destiny), though you can equip more than one legendary item.
Aside from weapons there are 6 other gear slots.
-Vest
-Backpack
-Mask
-Gloves
-Holster
-Kneepads
There are basic set types available but I don't know anything about actual Epic or legendary sets being available at the moment. Most of your loot drops fall into one of the above six categories and until you reach higher levels (25+) are generally blue items and can be moved around at will. Like Diablo, the item doesn't really matter until you hit the level cap and begin building your gear to match your play style/needs. So the whole argument about being able to change talents/abilities around, leveling them all together is really moot as your gear is going to be the final deciding factor where your play style is concerned. Gonna be a medic? A max level seeker mine, shield or DPS buff ability means nil because your gear, talents and weapons are going to be used based on the buffs they give to your medical abilities.
From what I understand right now, End game content is limited to dailies and farming the DZ for better gear (though there are only a handful of players truly in end-game content already. Sad for them for rushing it). The higher level areas of the DZ are full of mobs and roaming groups of mobs that are 2 levels higher than the current player cap. They easily wreck 1-3 man groups who aren't paying attention and cause massive disruptions for players already engaged in a fight that they wander across.
For the first real push of a tactical shooting element into the RPG world it's really not a bad push. Of course there are things that Massive can improve on and I hope they will, in time. Writing it off as a wanna-be Borderlands or something of that ilk is not even giving it a chance as it does what it does better than Borderlands could ever hope to do and takes a fair amount of lessons learned from Destiny and Diablo. The only lesson it apparently didn't learn from Destiny was how to not make the daily missions (On a difficulty above hard, which is "Challenging") a complete grind fest. I'm not there yet but on the other forums I frequent there have been some notes written about the "challenging" missions.
) - just wandering the streets is (almost) worth the price of admission IMHO.
