I actually play dark angels, and here are my thoughts on your list, And as a note most of those I play agrees that I can use the ordinary marines wargear, so my apothecary grants FNP, my power of the machine spirit can shot better and my stormshields grant me a 3+ invu save always. I don't know if you are allowed this, but it makes alot of sense to those I play and myself. Its all about asking;)
I can see why the other guys are suggesting that you only use belial or sammael at a 1500 point game, and I will say that they are right.
I tried some time making a dual wing, but I always end up wanting more than 2000 pts worth of models, so I would try doing a mono list(deathwing;)) at this point lvl.
For you list I would skip sammael, just as the other guys say. He really aint worth his 205 points and the apoth for 3 models, aint worth it either. If you want him you should use more points on bikes. Maybe just doing a full unit of 6 bikes, instead of 2 of 3 just to make sure the apoth can save his points.
And further, the other apoth, for the termies, throw him away. You allready have a 2+ save, you dont really need FNP too. Most of the times people will just focus all their ap 1 or 2 at them, and they are gonna die just like any other terminator unit.
When I do deathwing terminator squads, I do them in 2 different ways. The first is a deep striking type of squad.
DS DW Squad
the point is that they DS down and shoot alot around, and the stormshield is there to take some ap 1 or 2 shots. Later they just start running around shooting and killing every stupid enough to get within 12".
My other kind of squads are focused on cc, and I usally put them in a crusader, I can see your not doing that but I will tell you about it any way;)
LC DW Squad
If you want them to bring even more death, just give them the banner and an chap in terminator armour. Everything will die to this, everything!
And now for the ravenwing. This was actually my favorite when I started playing DA, but above 1000 points I had a hard time getting a pure ravenwing army to work. I think that you are making you squads to small, when you lose the first model with a melta gun It cost the same as the attack bike, you have to buy the extra 6 bikes if you want to buy any weapons for them. And I don't think you should count on 3 bikes making it to late game, If your oppenent gets the first turn you will have 6 bikes, 2 attack bikes and maybe sammael on the table, and even though they got the apoth, they will be gone very fast. I would suggest one full squad with 6 bikes, attackbike and landspeeder instead of 2 small, you can always combat squad them.
And for the last part about the attackbikes and landspeeders seem to be scoring no matter what, I would agree when looking at the RAW, but Im sure its not the RAI keeping in mind its a 4. ed codex and all.
That was alot I had to say
Hope it helps you