There's a dreadful feeling one can have when wanting to play a game but not being able to: Like a horror game that's too intense or a fighting game when on a losing streak. In the case of Back 4 Blood, it's the toss-up between having an alright time versus a frustrating and unsatisfactory play session that leaves me tenser than a freeze-dried mattress spring. Granted, a good portion of my upcoming criticisms may not be an issue for others since everyone's online experience varies, but mine so far have been overwhelmingly poor.
I won't rob credit from the game where it's due, as I really enjoy the card-based system. It encourages building a deck that fits your gameplay mood or playstyle. Building multiple decks ensures that you can still contribute in your particular way if your preferred character isn't available. For example, I have a melee-focused deck that temporarily sustains my health and does empowered healing. Yet also an LMG-focused deck if I want to spray a wall of lead and rarely worry about running out of ammo. Yes, getting to the good stuff can take a few runs to earn the required supply points, but I wouldn't call it 'grinding': Completing levels gets you points at a steady rate (especially if there's a bonus objective), so through regular play you'll eventually build up a stack of points to go shopping with.
That is when the system is working reliably. When you join a run (Back 4 Blood's term for the campaign) in progress, you're meant to draw cards from your deck up to that level so you're not behind and underpowered. Regardless of whether you take over a bot then get to the safe room or start from it, there are times the game will either not give you those drawn cards, or you'll be stuck with that bots' redundant deck. Starting a new run from scratch is the best option to avoid this, though that gets incredibly tiring if you want to visit new or later levels that were already unlocked.
Cooperative multiplayer games without a regular group can be a gambit on how much fun you'll have with random players. The first warning sign that Back 4 Blood can live or die based on who you're teamed up with is that (at the time of writing) there's no apparent way to kick someone who's harassing, idling or purposely trolling. There's a report function, yet that will not fix the issues you're currently having in that play session. Besides, I'm skeptical that repercussions will ever get levelled against offending players. This gets exceptionally irksome because hazards can alert the horde if they're struck during levels. Despite the dangers of doing so, many players can (and actively will) set them off, causing an already challenging game to get that bit rougher for the next few minutes.
Playing solo with team AI isn't an entirely ideal solution due to how the AI will range from quick crack shots to being dumber than a bag of bricks out of nowhere. From my experiences, it appears that they can hold their own during small to medium skirmishes, but once things turn into large hordes and specials arrive, their decision-making gets muddled. For example, I've lost count of the number of times I've seen an AI teammate training their sites on a Tall Boy approaching while completely ignoring zombies sucker punching them in the kidneys. My favourite instance of the AI failing is when I was hanging off a bridge with a Hocker in the area; instead of rescuing me or going for the Hocker, the AI just wiggled back and forth, eventually getting pinned down and losing the run.
While I'm no esports legend of yore, I'd call myself an experienced and average-skilled FPS player. I mention this because Back 4 Blood can slap you upside the head if the campaign director feels like ruining your day even on the lowest difficulty. The nature of zombies and specials means that if you're surrounded and spot a special approaching, it's often a net loss result: Focus on the enemies immediately around you and allow the special to attack, or focus on the special and have your health be chipped at in the meantime? Made worse is that telling apart certain species of specials isn't immediately possible at a quick glance. For example, Exploders, Reekers and Retches have chunky, thick wide models. They can be told apart when analyzed but in the middle of a heated battle? Forget it.
There are times where the level design encourages splitting the team up and leading to catastrophic results should enemies that can bind or pin (Crushers, Sleepers, etc.) appear. Levels mainly consist of directing or funnelling the team from point A to B via visual cues, but there are places where that design philosophy gets flushed away. For example, there's one level in an industrial treatment facility where the team has to destroy nests and trigger hordes to locate a key. However, it's a large open area with multiple directions to run off in for the sake of the objective and side paths for potential bonuses. As you might expect, deviating from one another based on interest/preference is bound to occur - I've suffered many defeats in areas such as these. Just because there's text/voice chat and pings for communication doesn't mean people will acknowledge them.
When you have a group of people you know or strangers that end up clicking, the game utterly shines. Solid combat and gunplay can be marred when zombies stutter or blip past your attacks thanks to server hiccups, but supporting one another, carving through the horde, and sweeping locations for loot is great fun. While precision weapons can feel ineffective unless racking up weak spot hits, all guns feel viable regardless of their tier. Doubly so if they have mod slots to further expand their efficiency! Heck, you can assist teammates indirectly by spending gathered copper at safe rooms: Old weapon mods or items you no longer use will fall to the floor, allowing someone else to pick it up and save up for other purchases.
[Spoilers for the finale in this section.]
It's all wrapped up in a messy bow thanks to the campaign finale, where it's a three-staged boss fight that's woefully shoe-horned in. All three stages require waiting or repositioning to attack weak spots that'll reveal themselves, but hordes and specials will continue to funnel in to interrupt said attacks and make things way harder than needed. The final stage has an attack that can instantly down you, but it doesn't appear to have an animation or tell; you'll be firing away and then oopsy doopsy; you're bleeding out on the ground. Oh, and the final stage is timed! What fun!
It's a shame that most of Back 4 Blood is frustrating or allows and encourages players to be frustrating. The gameplay and mechanics themselves are fine, but it's like Turtle Rock Studios assumed that every lobby would get along fine and not require any means of handling issues. So again, your experiences will likely vary from mine, but as it stands, I can only recommend Back 4 Blood if you have at least one other friend to make a team with. Even then, out of all the co-op games I've played, Back 4 Blood has cemented itself at the bottom of my preferred list.