It's obvious someone doesn't play Space Marines, ya ruddy git.
Ah on the contrary good sir I do play Space Marines.
I have never once lost my army before they have engaged the foe. Their armour pretty much is the equivalent heavy cover and if you use your force tactically in accordance with the map, instead of making a beeline towards the enemy, then it makes things a lot easier. Using fast attacks, scout biker squadrons for drop pod beacons, biker squadrons, land speeders or even if you just use a Rhino or Razorback to get your troops in, makes a lot of difference as well.
Playing as the Astartes is all about striking the foe in a movement of swift retribution and if you fully utilise the armaments of the Space Marine Arsenal this is
very possible.
Unless of course you meant that
you don't play Space Marines and in fact play Orks.
Oh and on track with the thread, I agree with the suggestion. Even though Space Marines move in Power Armour like it is their second skin it is realistic to assume that they must appear very bulky and this would be reflected in their movements. It is aesthetically pleasing as well.
