The Dark angels have only one entry in the Troops portion of the codex.  The good old rank and file tactical marine squad. However, we have our Ravenwing and Deathwing units that can lend support as Troops as well.




Tactical Squad:
First, let's talk about the obvious disadvantages we have.  Unfortunately, our tactical squads are more expensive than stock marines.  Spending points on equipment that other marines get free is especially frustrating.  Also, our marines lack combat tactics, which makes them a little worse on their own.

However, the good news is we have ways of boosting our tactical squads as well as a couple of small things working in our favor.  First, we have more options than other marines for making our tacticals hard to break.  We have the sacred standard for one, which can make them fearless.  Fulfilling this same role, there is also Ezekiel which acts similar to a sacred standard, giving us a Fearless "bubble".  Of course, the obvious boost we can take is Rites of Battle.  This one is the easiest and potentially the cheapest option as well.  I have had Rites of Battle save me in several games, and I'm sure it will continue to serve me in 6th (at least until we get a codex update).  These boosts are huge, but unfortunately, they require other units to confer this bonus.  I like to think of the Dark Angels codex as a book of combination units, and for list builders, maybe this will help.

We also have the fact that our smaller squads can take special weapons.  This is not a huge advantage, but it does make smaller 5 man squads feasible without having the need to combat squad.  While not huge, we can spam special weapons better than most other armies (with perhaps the exception of Wolves).  The ability to take 5 man squads with a special means we can take a squad with a special weapon and a sergeant with a combi weapon without needing to waste points on large squads.  In an edition where plasma spam is resurgent, this is a nice little trick, and I'm sure I will build at least one list like this just for fun.

Finally, we already discussed the fact that Deathwing and Ravenwing can be taken as Troops.  But I think this helps our list a lot.