I am actually Interested in your list Ben see what you ran as Space Marines. I am doing a complete overhaul on my Army lists so I would love to know what worked and didn't for you.
The list I ran is the army I built for teaching, so it ain't no great shakes.
Librarian, Terminator Armor, Storm Shield (woefully under used, need to research psychic powers)
Terminator Assault Squad, TH&SSx4, Sarge w/ Lightning Claws
Thunderfire Cannon x2
Devastator Squad, ML x4
Dreadnought, MM, DCWW w/ storm bolter, Drop Pod
Dreadnought, TLLC, ML
Tactical Sqaud x3, sarges w/ power fists, two rhinos, 1 Razorback
Scouts x5, Camo Cloaks, ML, Teleport Homer
The Librarian and his squad actually worked really well. They held off Typhus and 20 plague zombies (and by every right the Librarian should have killed Typhus twice). They won the secondary objective in the second game handily, never had to worry because they were so solid. They were gunned down in the third game but even the Librarian still lived, giving my army a chance to move into position at game end. I took it on a case-by-case basis, but thought it better to Deep Strike the squad each game. It seems good to have that option.
The Thunderfire Cannons were honestly hit or miss, but for their points, I'd take them again. And with the Devastators, that can be 12 small blasts I'm throwing around per round. It can add up, with some luck.
The shooting Dreadnought had minimal effect. The Assault Dreadnought, I'd take again in a heartbeat. Coming out of the Drop Pod allowed me to react quickly.
I didn't utilize the Scouts well enough, nor the Librarian's psychic powers.
I feel like if I had spent time on a list, toward optimizing it, I could have won two games. There was nothing I know of with which I could have stopped Dean's list full of AP 3 balefire. It's a hard, hard counter.