It wasn't possible to concentrate fire as the direction of the Ork attack was not known, so it was necessary to create lines of fire in all directions. The Orks, not normally known for their tactical acumen, surprisingly launched a ground attack from the West while bring air units in from the East.
A Dakkajet and DeffKoptas attacked Brother Lacus and a Deathwing squad as the mounted units crashed into the defending Marines.
Taking casualties all the while, the Dark Angels were able to reposition and eventually destroyed two Truks and Battlewagon, Orks spilling onto the battlefield from the wrecks.
Boltguns, lasguns, and fists chewed through the Ork ranks, but their numbers were massive.
Meanwhile, a huge mob of Boyz and Nobz attacked the second squad of Deathwing. Although the Warboss was killed, even the mighty terminator armour was unable to withstand the prolonged assault. Deathwing Sgt. Gladius was the last standing, holding against the rampaging horde, and died a heroic death giving honor to the Emperor, as Orks poured into the ruins through gaps created as Astartes died.
Finally, the perimeter was reduced to just the space inside the ruins with the remaining Space Marines assaulted on all sides. Though they had lasted into the 5th turn, with Devastators continuing to pour fire into the masses of Greenskins, their plight was now hopeless and they were killed to a man. The savage Orks had succeeded in wiping out the beleaguered Dark Angels.
So, this scenario was a lot of fun and not quite as one-sided as it looked from the beginning. Not getting to shoot in the first turn really hurt and I failed a LOT of armor saves. Still, it went fairly well and was a lot of fun. Deffkoptas SUCK. As in, they're really good. Having units deployed in open topped vehicles is a challenge as well. You have to target the vehicle and not the mounted unit, but the mounted unit can fire out of the vehicle in addition to the vehicle firing its weapons. And the vehicles have a lot of wounds, making them hard to destroy. Also, if playing this scenario, I would recommend using defensible terrain as close to the size of the defensive deployment area as possible so the entire army can benefit from the cover afforded from shooting.