All I'm saying is that if it was a scrim at my local store I'd have been able to at least take out a couple marines by playing smart instead of turtling.They had no chance they where dead as soon as the astartes boarded the ship, they knew ecaxly what they where doing and they knew exacly how the fight would end up, this is guys with hundreds or thousands of years of experience and in the very little time they are not deployed in warzones all they do is pray, study, train and prepare for war they study every single threat and how to kill it.
If the astartes even thought there would be issues they would have brought proper anti psyker counters i mean a single sister of silence would have wiped the floor with them, but this strike team have propably done this a hundred times you could see how they just casually moved on after killing them like they just slapped some children around.
This was alo just the mopping up operation of a rebellion so most likely low level psykers not like magnus the red who can obliterate battlefleets in orbit while standing on the planet bellow.
Think it's suppost to show how insanely good they are at what they do i mean how can normal guys ( aside from the psykers) fight religiously indoctrinated from childhood, genetically modified transhuman warrior monks, each with a century of experience in war, clad in a millenniums worth of technological advancement, and personally armed with fully automatic micro-rocket launchers. Unendingly tireless, preternaturally fast, impossibly tough, supremely intelligent, precise, efficient, and completely and unsympathetically zealous in their devotion to the task at hand.