If you're a Power Armour wearing Space Marine hugging corners just isn't an efficient way of fighting. If your armour and physique can take such hits why not use that advantage? You're talking as if the Marines are walking around naked.
I'm talking as if he just walked into firing range of a heavy weapons platform. That could have been a lascannon, a multimelta, whatever.
For a "highly trained" super soldier, he walked right into what should have been a death trap. He just got lucky that it was a twinlinked multilaser, which still puts out 6 Str 6 shots, so... Could have been deadly. He could have at least checked the corridor before he entered it. It was clearly close enough that he could fire a plasma pistol and kill them.
Chances are that he couldn't even see the heavy weapon platform until he was a few steps in the corridor so checking around the corner wasn't even possible. They clearly waited until he walked a few steps and got good aim at him before revealing themselves. Also he was kinda busy dealing with all the other soldiers in the corridor already when he got in range. Yes it was a deathtrap and yes he got lucky but I don't see how it was necessarily his fault. A good trap is one you don't see coming, otherwise it wouldn't be much of a trap.
And the "6 Str 6 shots" has literally no meaning. That's purely crunch which doesn't representate fluff that well most of the time anyway.