There is honestly absolutely *nothing* wrong with bullet sponges. The reason why this game is not working is because it's *not* a typical RPG with a holy trinity system.
The game has a threat mechanic, which means you are actually supposed to be able to "tank". Supressors and Vent Brakes are useless right now and the video I linked is the reason why.
The Ballistic shields adds "threat" but you can't tank with it (they would have to buff it by around... 1000%? supressors aren't needed either because NPCs don't "aggro" like in WoW.
Bullet sponges would be alot cooler to defeat if you have to work around something like that.
Tank lines up the targets, you use cover to cover to flank them, you use supressors so that they won't aggro you while you empty 2 magazines.
Stability and accuracy becomes much more important because you want all your bullets to hit while you unload your magazine. SMGs become Burst weapons, ARs DPS weapon and MMRs Long range Support weapons. Shotguns/LMGs/Pistoles become Tank weapons.
And you can *clearly* see that this is exactly how they tried to design the game, but they failed to do it.
LMGs supress enemies, so they deal less damage to you, it won't affect DPS because they are supposed to flank targets behind cover and unload their bullets from the sides. Supports need to be everywhere at once, Heal the tank, support the DPS, this is why they could use MMRs, all the abilities have a rather high range after all.
Due to how the maps are designed, they could actually add something like "+% dmg if you use a elevation" (as a sniper for example)
ARs can have balanced and are extremely accurate. SMGs could burst down "smaller" adds (Purp-"elites" for example), or they could benefit from the +% damage after the cover to cover move more so than ARs and be some kind of a weapon for a player that likes to be "mobile" while doing his dps.
LMGs could also help pinning down a target that is being flanked, so that it doesn't switch positions and your DPS can keep shooting at him
In the end you could have had a group of 1 DPS, 1 Support, 1 Tank, 1 DPS/LMGsupport.
Instead of 4x DPS with SMGs, or 3xDPS + 1x Support/DPS with SMGS/MMRs
that would have been so - much - better and actually the way I thought the game would play out after the Beta.
"Oh man, I'm going to use this ballistic shield, with a really good pistole and tank (with threat management) everything while you will use your LMG to support me and you two guys will flank them and wipe them. I can only imagine how cool the talents will be that'll help me tanking"
That was pretty much the impression we had about the game when we left the Beta.
Look at the "pulse targets that shoot the ballistic shield" perk... I thought "Wow, I can buff DPS damage while tanking everything - thats how playing a tank should be!"
Turned out it's flipping useless.
edit: Oh man... just thinking about all the possibilities.
Imagine if CMS only had like 3-5 Elites per encounter, which need to be tanked by the tank. Additional adds are low dmg + relatively (but not absurd) high HP purples that need to be dealt with so that they don't use grenades / abilities / buffs that will annihilate the tank (flame grenades, first wave agents, riker "leaders" that rile up the elites to deal more damage)
These 3-5 elites however could deal so much damage, that you *need* a tank or you will end up like in the short video I linked and tanks should actually be able to hold their own against them.
Once you cleared all the small fry you will then proceed to kill the Elites, one at a time, or sometimes 2 with AoE (grenades, sticky bomb) abilities. You have your LMG guy supress a single target so that it doesn't move, your DPS will then deal damage to it, rinse + repeat.
Sometimes the elite will break supression, move somewhere else and have some kind of "aggro reset". In fact they could announce it somehow (similiar to DA:I where they scream "FOCUS THAT WARRIOR") they will then move around and supressions just makes it so that they will do so a lot less frequently, the tank will then try to grab it's attention again and so on and so forth.
The tank won't do all that tanking by just standing around, he has to move around too so that the elites need to have a proper line of sights, the arena is always pretty big, there is a lot of cover everywhere, he would "kite" them around while managing threat or disabling one of them so that he can move closer to where he wants to be etc.
It would give the "rusher"type-enemy a new purpose too, he would constantly force the tank out of cover and is very hard to pin down by a LMG so that you don't want to focus him first or something like that.
All that is impossible or rather a extremely stupid thing to do, because they decided to make content more difficult by increasing NPC damgae and not allowing you to increase your own survivability.
Why would you use anything but a glass canon with high DPS, when going full tank will only make you last 0,5s longer.
TL;DR
game is worse than it could've been