No, Did I say that? I said that actually HITTING that Marine in Melee with a Power Sword is very slim. Remember Space Marines have the speed and reflexes far beyond what ANY human is capable of.
It says that most Regiments do that, not that all do that. It even mentions a split in the Mindset of the Generals, one that only care for the Quantity of their Soldiers, the other one caring about an quality army with a much bigger battle Value then the Number of it's Parts. You get told that the most common tactic is the Human Wave and most Commanders are extreme ruthless. But also that there are Quality Regiments, spec ops fighters and Battles where the Guard stood outnumbered against overwhelming Odds without much casualties.
Usually plot armored groups though right? I mean Gaunts Ghosts is pure plot armor from start to finish. There is nothing about them that is special that's what no one seems to get here. If those characters got hit in the chest with a Bolter Round they would literally implode and thats the end of the story. I don't think you should base what is acceptable on Plot Armor rather than their actual in universe capabilities.
So, it is possible. And this is a game. Guardsman & Marine will have the same reflexes, or am I missing something?
It's possible in that if the Marine was completely unaware and standing still then yeah you might have a chance of killing him. In practical terms god no. They will have the same reflexes because it's player reactions but we're talking about why IG are so weak in fluff. Also a Human will probably straight up die from a single melee blow from a Space Marine, where as it will take a decapitation to really stop a Marine in one blow (Good luck reaching up to the next).
Actually, marines aren't all that fast. I am fairly sure that guardsman have initiative 4, which is equal to that of marines. I could be wrong however (I don't use guard, nor do I know many people who do), and if it is I 3, than they would hit a little slower. A marine is slightly more skilled in CC, however not enough so to make it significantly harder for a guardsman to hit him. The only real difficulty is in the guardsman actually hurting him, and then the 2/3 chance of it being absorbed by armour Also, I am going to continue advocating balance based on the table top game, because that is what the lore is based on, and it is an example of a currently working game that uses these armies. And you really need to remember, the lore is based on the game, not the other way around. Most codexes will puff up their army (most of them talk about how the army will slaughter most opponents with little difficulty, so they basically conflict with each other, as well as the actual rules of the game), so you need to take what you read with a grain or two of salt.
If you mean assault marine, that would be.. harder. But if catachan with powersword engages devestator...You'll probably see devestator dead in a seconds.
I don't know how many times I have to tell you that I'm talking about Fluff not Table top which makes zero sense in the context of said fluff. Find me once instance in the fluff where a Guardsman is as fast as Space Marine. Also Guard is the only codex which says "Yeah we suck, but we have more than you do".
And I don't know how many times I have to tell you, but according to fluff it is completely, 100% impossible to have fluff based PvP, unless it's marine combat training, so they are mock-fighting each other. Because a single company of marines in fluff would probably be able to kill a couple of Eldar Craftworlds, an Ork Waaagh or two, and defeat a Black Crusade, and only take about 5-10% casualties, if they were unlucky. According to fluff, this game should not exist. And, again, this is why I am saying balance should be based on the rules, where there are quantifiable stat lines, rather than books which would require interpretation, and sorting through "We are teh bestest army evah" bias.