Oh yeah the one dead marine from a full rapid fire lasgun volley. Yeah that's really shooting them up.
I'll give you the Ork argument. One of the issues I have with TT marines is that they don't have enough close combat attacks (why I prefer the Space Wolves codex hands down). Space Wolves hold up much better against Orks in close combat. The key of course is to shoot the hell out of a mob before engaging it in CC, which is in fact very fluffy. And nowhere does it say that Space Marines can just wade through Orks without difficulty.
As far as the boltgun goes I'm curious what you think it should do. As it is it kills lightly armored enemies very efficiently while dropping off against heavier troops. That's pretty much what the background says it does. With all your talk of what guardsman squad does shooting at marines, it's only fair to point out that a squad of marines rapid firing on a guardsman squad generally doesn't leave much alive (one or two guardsmen at most).
I can't help but think that you're one of those people who think Marines should succeed simply because of how uber they are. The truth is that they are highly skilled tactically which causes their inherent superiority to be multiplied through precise application of force on the weak points of the enemy. Don't get me wrong they're toned down on TT, but not to the degree you and others seem to think.
Even if its just one dead marine, thats still grossly inaccurate compared to the fluff where Space Marines wade through seas of las fire. Astartes are compared to walking battle tanks, however on the tabletop they're more like guys with decent armor.
Space Marines tool on Orks just fine in Rynn's World. 10 on 10 in CQC tends to favor Orks on the tabletop.
The boltgun is often depicted as being capable of penetrating power armor and being used as a makeshift sniper rifle. Range 24" and AP5 does not correlate with that, but then GW seems to have no idea of how a sniper rifle really works anyway.
Every bit of fluff shows Marines holding out against odds incredibly against them - a handful of marines win a battle, a company of marines take down over a 1,000 Orks, etc.
I've never seen this represented on the tabletop aside from Movie Marines.