As a genuine greatsword expert, I honestly don’t know where to begin. I’ve gone over so many times why I disagree with the idea that the weapon is weak, that it kind of gets tiring.
I’ll start off with armour first, and I’ll actually say that armour - is not as significant a threat in this game as people would like to believe. Half of the elites in this game are completely unarmoured, such as Chaos berserkers, plague monks and maulers. The latter of which is about as common and arguably more annoying than Stormvermin, and the former being deadly enough as to warrant shotgun builds primarily just to deal with them fast and efficiently. Greatsword actually shreds both of those. Genuinely one of the highest DPS weapons against massed clumps of maulers or berserkers. Not only that, it’s an extremely safe weapon to kill them with, since the wide sweeping heavies will cleave through anything that’s in the way and control/kill the chaff, and occasionally stagger these elites.
Stormvermin don’t have that much health, they’re genuinely pretty squishy, and they’re easily staggerable. What it comes down to is the wrong technique in dealing with them. Never just spam push-attacks, it’s a waste of stamina, and in my experience it’s an actual loss in damage and safety. When fighting armour, instead alternate between Heavy 1 and Push-attack. Heavy headshots and Heavy crits stagger Stormvermin. Staggered enemies are more susceptible to stagger, which lets a simple push stagger them even further. With Mainstay - that’s 60% more damage. Directly after the heavy attack you headshot with a push-attack. On Legend this 2 shots a singular lone Stormvermin on Legend last I played on that difficulty.
So what does this actually mean? That Stormvermin hordes are incredibly simple to fight with greatsword if you alternate between heavy and push-attack. No, you’re not staggering the entire horde like with a shield, but it does make it incredibly easy to dodge and kill, since they stagger easily. With Mercenary I cleave like 5 Stormvermin, stagger around 3 of them, dodge the other 2, then push-attack (which by the way is incredibly easy to get headshots with due to the angle of the attack) and actually deal good damage against armour. I say this with completely certainty, that I would rather fight a Stormvermin patrol with a greatsword, rather than an executioner sword or even halberd.
The weapon is just great against mixed hordes. It’s incredibly easy to use since you just need to spam heavies, the attacks have a wide sweep angle hoovering up everything in front of you, and it cleaves through just about anything, meaning no berserkers can hide behind Chaos Warriors, or any slave rats behind Stormvermin.
The mobility it has is a huge advantage over something like the executioner, having 50% more dodge count and 10% dodge range. Combined with the stagger, it’s very ergonomic when handling hordes solo.
It works well with most of the careers that can use it, like Mercenary, since the huge raw power% boosting damage, cleave and stagger simultaneously, which greatsword (in my opinion) benefits disproportionately more than most weapons in the game, and always having permanent Paced Strikes (something that I sometimes miss when using something like halberd). It’s not good with Huntsman or BH, 2 ranged focused classes, which I think is perfectly acceptable.
What are my credentials? 1700 hours in the game, many of those hours having played Mercenary with greatsword since the literal start of me playing this game, going through Champion to Cataclysm and beyond with it.
Do I think the weapon needs to be buffed? No, I unironically think it’s actually good, I just simply can’t have any other opinion when I’ve used it this much and compared it to other weapons. Do I think it could use changes? Yes, it’s a rather dull weapon in terms of its moveset, and I’ve done topics in the past on what precisely greatsword could use to make it more fun (the topic was on the Beta Feedback section of the forums, which is now forever gone, but maybe someone will remember the paint illustrations I did there). Yes, give a new function to light attacks (not armour-piercing though), add some sort of mordhau attack, etc. Anything but a buff man, please.
Here’s a comment in the past that I made going more in-depth on the stats of the greatsword: Kruber - Greatsword vs Executioner's sword - #4 by Rebel
TL;DR - greatsword good.fight me nerds