If you want to stack armor, she's one of the best for it, with one of the highest base armor among shotguns. That combined with her skill, she can easily hit some insane armor thresholds, making her take 1 damage (zero with flash rounds) where other shotguns can struggle. This does come at a price of having her HP be on the lower end of shotguns.

However, there are now plenty of other options at this point in the game that can produce similar, but better results. That doesn't make her trash, but yeah. Still usable.

The other shotgun besides KSG that has +Armor skills. Has higher HP and really good armor, but has an offtank aura meant for 2-shotgun formations which means you'll either need to move her every fight or have another shotgun. The aura effect is less flexible than a firepower buff, but potentially useful buff to a lot of MGs like M2HB or PK who could really use an acc boost. Regardless, If the primary consideration is just sheer defensive power, she makes an decent pick.

MURRICAN SHOTGUN. The most usable aura of the 3 star shotguns currently on EN, though forcing her to be in an offtank position. 21 armor and a +armor skill. There's really not much to say about most of the shotguns besides "they'll do work if you really want them to."

Also a better catgun than IDW. IDWSG DA NYA.

She also has a mod, and the review for that can be found here.

Despite having the lowest armor among the shotguns (tied with Captain China), her skill offsets this a bit. Also has the lowest HP among the 4 star shotguns though, but whatever, she can still take hits. Her main downside is the shitty aura, but she can at least do the job of eating hits.

3* Super Shorty. Better tiles and more HP, one more point of base armour but less evasion and lower skill multiplier kinda comes out to about equal tanking capability. Which isn't all that great, but at least she's free.

She has Python-like activation requirements to pop open free shields, which can be useful for some situations. YMMV overall.

OK, your mileage may vary a lot for this one. Her Armor isn't great and she herself isn't exactly super tanky without her skill up. On the other hand, her skill might buff your other shotgun(s), so it may be useful for that.

OBEY. Made from a less-lethal shotgun meant to give police forces more options to put down people without killing them. In G&K's case, however, she certainly helps with takedowns.

Incredibly good stats for a shotgun, good formation buffs, and her skill has the unique ability to cancel enemy buffs. These buffs include ENEMY SHIELDS (including Patroller shields) and stat buffs (including bullshit enemy evasion buffs). Her mechanics are unique, so she actually ignores normal knockback immunity. Oh, and her armor buff stacks are multiplicative. Unfortunately, the Minotaur's damage reduction is a weird thing that can't be removed, but regardless, you get so much utility from her. Even if you don't need her skill, her stats are just that good.

If you don't have her, get her from a True Core Mask or something. She's just too useful in things like later Theater events.

Supernova is a shotgun pretending to be a handgun to go along with her shipmate GSh-18. She’s one of the most supportive shotguns available and she enables some real dumb stuff. You want to use MGs at night? Well, her skill allows for that. Do you need a little more defensive capability for your shotguns? She brings that too, all in a kancolle-flavoured package. Honestly, she’s not an automatic pick on every team. You’re likely going to have to drop a MG in your formation to make use of her fully, which can be an issue.

Her two main draws are her movement speed and her MG buffs. Her roller skates allow her to go almost as fast as a handgun, but not quite. Not much else to say about that, but main reason to take her is the MG buffs she provides.

While crit rate is nice, the accuracy buff she provides to MGs is fixed. This means that MGs are entirely usable at night. It bypasses the accuracy penalty that you would normally have with no PEQ. While not the most relevant thing currently, you definitely want to have Supernova in your back pocket for the future.