I have discussed the Dark Angels special characters in their own entries.  Now I will talk about the other characters in one entry.  Dark Angels stock characters do not suffer from the same deficiencies in relation to the vanilla marine codex and in many cases are better.  The obvious standout is the Interrogator Chaplain, who in my opinion, is the best choice among the stock characters.

Interrogator Chaplain/Chaplain:
Codex: Dark Angels includes two chaplains that players can choose from and I will discuss their merits in one entry.  Back in 5th Edition, the basic chaplain was very much a stock choice for me as they are better than their vanilla marine counterparts and are less points than the Interrogator-Chaplain.

Both chaplains (the Interrogator-Chaplain and basic Chaplain) are exceptional characters, and both will probably still make their ways into many lists despite the nerfing of the Crozius Arcanum.  Simply put, you get a character that increases the melee effectiveness of any unit he joins by 1/4.  He also has the added benefit of making the unit fearless, which as we know is simply amazing in 6th edition.

Of the two choices, the Interrogator Chaplain almost seems like a gimme to me in 6th edition. For 20 points more you effectively get a special character level stat line as well as unlocking the Sacred Standard which makes even more units in the army fearless.  And this upgrade wargear only costs 5 points more!  Of course, the other benefit to taking an Interrogator Chaplain is unlocking Terminator armor.  Unlike 5th edition, the protection afforded by Terminator Armor is huge, and I for one can see me dusting off my old Terminator Chaplain for use in games, as he has become worth the points again.

The basic Chaplain is cheap and honestly he is better than his vanilla marine counterparts.  His upgraded stat line compared to vanilla marines still makes him a viable choice.  While true that you lose the access to the sacred standard and terminator armor, he is a good all around choice if you are trying to save points and just want a cheap HQ that still gives you a good amount of punch.

Company Master:
Dark Angels Company Masters are not nearly as good as their other codex counterparts.  They are expensive for what they provide the army and do not have access to a lot of new and shiny wargear available to their counterparts in other codices.

Despite the deficiencies, I found a place for Company Masters in my lists several times for one big reason: Rites of Battle.  Rites of Battle was a huge boon in 5th edition.  This was basically GW's answer to Dark angels losing stubborn.  And, since I always loved the fluff of the intractable Dark Angels army, I found myself fielding these guys really often.  In a lot of games Company Masters beat out Belial as a choice simply because they could be transported in Rhinos and Razorbacks and because I could customize their armament a bit more than Belial.  Speaking of wargear, thanks to the FAQ, the Company Master could also be armed better than a basic vanilla marine captain, albeit with less options in wargear.  He has no restrictions on his wargear and if you can model him to have a pair of lightning claws and combi-melta, you can arm him that way.

Unfortunately, the master's major drawbacks are his limited selections of wargear.  He can't take terminator armor or a bike for one. And, he lacks a lot of the best wargear available to vanilla marine captains.

In 6th edition, I honestly see the Master making it into my list far less often than before, as I find Belial better in every aspect and will be using Rhinos and Razorbacks much less often.  The only other thing that the Master does that Belial can not, is unlock a Company Champion, but I hardly think that small boon will make him more appealing than taking Belial.  I will miss fielding my converted master though...so, I'm sure he'll still make it out on the field of battle from time to time.

Librarian:
The Dark Angels Librarian almost never found its way into my lists.  I tried them a few times in 5th edition, but simply found Hellfire to be too unreliable.  Simply put, the little they offered with their powers, I could simply do better elsewhere in the army.

I think we may see more librarians fielded in Dark Angels armies in 6th edition, but I for one will likely still not use them.  I like the fact that the librarian is more of a combat monster than his vanilla marine counterparts thanks to the upgraded stat line.  However, coming in at the same points as an Interrogator Chaplain, I just do not see myself justifying taking a librarian even with the ability to take the expanded powers available in 6th edition. 

All that being said, the Librarian is still a formidable opponent.  He can be armed with the "better" power weapons instead of being stuck with the AP4 power weapon of the Chaplains.  and, of course, he can cause instant death which now has the added benefit of being the only thing that can beat Feel No Pain.  Also, the Librarian has one small advantage over Ezekiel in that he can be given Terminator armor which gives him access to an invulnerable save.  I personally will use these guys very little, but I still think they may make a good choice for a lot of players.