I think what's going on here is simply that they're trying to make things different. See, every time a codex comes out, people whine 'why can't my army have this?', so they're changing it. I really feel that they're making Deathwing (and really, all Dark Angels) a 'take and hold' army. It explains why their bonus is overwatch. You send Ravenwing in early, using their strength as scouts to rush ahead, and on turn 2 (or 3, or whenever you feel like it after you're tactically in position), you bring down terminators that simply WILL NOT BE MOVED. Shield wall. Full BS Overwatch. FLYING VINDICATORS.
Let the smurfs drop in blindly turn 1. The Dark Angels are now firmly set up as the army that uses their strengths. One squad scouts, the other supports. The Dark Angels have become a very powerful synergy army, rather than three distinct playstyles.
Now, with that said, so
doesn't feel like I'm throwing around too many rainbows and rending unicorns, I do think it's unfair that Ravenwing can be played on its own and Deathwing can't.
I do have ONE suggestion for you though,
. Run a Landraider Spearhead with your Deathwing. Because I dare
them to move three indestructable Godhammers off the table while you're waiting for turn 2.