So, as I have been playing around with how to make an efficient Imperium “firebase” that is not based around Guilliman and UM Razorback/ Devastator spam and is also durable enough to “take a punch” and still survive long enough to hit back (i.e. survive enemy Alpha Strike, if you don’t get first turn), one thing that jumped out at me is the efficiency of three particular Dark Angel units:
 Azrael — For only 36 MBs, Azrael brings A TON to a list, especially to a Gunline style list. Not only does he provide the usual Chapter Master 6″ aura of re-rolls for all to Hits, but he also provides a 6″ “bubble” of 4++ save to ALL friendly Dark Angel models (so this includes vehicles, characters, himself, etc., etc.). On top of this, he gives a “bonus” CP for being your Warlord, has solid shooting himself in the form of a Master-crafted Combi-Plasma that shoots at BS2+ (with re-rolls to Hit, of course), and is a VERY solid close combat fighter as well, with 5 x S6 AP-3 D3 damage attacks a turn, all at WS2+ and with the ability to generate Mortal Wounds on a roll of 6+ to Wound. Put it all together, he improves the offensive potential and durability of a Dark Angels Gunline, gives you more CP to play with, and can even serve as a strong “counter-assault” hero if enemy melee units get too close.
 Dark Shroud — Most people are already aware of how potent this Fast Attack choice vehicle is, as it gives all friendly DA units within 6″ the ability to reduce enemy to Hit rolls when shooting at them by -1… for only about 30 MBs, this can make numerous DA models significantly more survivable, especially when coupled with a nearby Azrael (so units get both the -1 to Hit bonus and a guaranteed 4++ save on top of their normal save). The Darkshroud itself is pretty survivable, with T6, 9W, a 3+ save, a 4++ Invul (if Azrael is nearby), and -1 to Hit it for any enemy shooting (i.e. on average, it would take 11-12 BS3+ Lascannon shots to kill a Dark Shroud, so your opponent will not be able to remove this “lynchpin” unit easily). Finally, the Darkshroud with an Assault Cannon can add some additional supporting firepower itself and, in a pinch, can “dash” out 13-18″ and grab an objective, if you are desperate at the end of a game.
 Rapier Carrier (with Quad Launcher) — A Forgeworld artillery unit (Heavy Support choice) available to all Astartes armies (except Grey Knights, of course), the Rapier Carrier with Quad Launcher only costs 17 MBs per model (this includes the two man Space Marine crew), is T5, has 4W, and has a 3+ save in its baseline profile. More importantly, it shoots at BS3+ and, with the Quad Mortar, has the option of using either Shatter Shells (Heavy 4, 24” range, S8 AP-2 D3 damage) or Thunderfire Shells (4D3 shots, 48” range, S5 AP0 D1, can shoot at targets not in LOS) each time it fires. As you can see, for the point cost, that is very potent damage output, especially given the versatility that the two different types of shells provide against a whole range of different unit types (the Rapier Carrier with Quad Launcher is kind of like the Deathwatch Veterans of fire support units I think). Obviously, even by themselves, a whole “battery” of Rapier Carriers can provide the basis of a highly effective fire base for your army.
So, now, how to integrate all of these elements into a single Battle Group? Imagine the following:
DARK ANGEL SPEARHEAD DETACHMENT
-Dark Shroud w/ Assault Cannon
-6 x Rapier Carriers with Quad Launchers
This entire battle group comes in at just under 900 points, so in a 2000 point game, you still have more than half your points left to either build additional elements of the Gunline, add in “bubble wrap” units, and/or create a potent assault or mobile element to your forces. Additionally, between Azrael, the detachment, and your “base” Command Points, this gives you 5 CPs out the gate, before you even fill out the rest of your army (i.e. you could easily add another Battalion for 8 CPs total or perhaps even make a full up Brigade with the remaining 1100 points, giving you a whopping 14 CPs!!).
Obviously, the idea with this battle group is maximize all the overlapping buffs of Azrael, the DA Lieutenant, and the Darkshroud to enhance both the shooting and durability of the Rapier Carriers. Looking at the two different ammunition types, we have the following average damage output when they all six artillery pieces are shooting with the buffs from Azrael and the Lieutenant:
24 x Shatter Shell shots at 24″ range–
**Against GEQs – 20-21 dead models
**Ork Mobz – 20-21 dead models
**Against MEQs – 13-14 dead models
**Against T4 2W Primaris units – 13-14 dead models
**Against TEQs – 10-11 dead models
**Against Centurions – 8-9 dead models
**Against Rhino-equivelants – 33-34 wounds (or 3 dead Rhinos)
**Against Land Raider equivelants – 18-19 wounds (or 1 dead Land Raider)
**Against Stormraven equivelants – 27-28 wounds (or 2 dead Stormravens)
**Against Imperial Knight equivelants – 24-25 wounds (or 1 dead Imperial Knight)
While the range of the Shatter Shells can be a limiting factor, if deployed properly and using the rest of your army to “funnel” his forces into the range fan of the Rapier Carriers, you can see above how devastating this firepower can be… basically, you can “one shot” a Land Raider or Imperial Knight every turn or, alternately, you can devastate multiple squads of medium-heavy infantry every shooting phase (you can split the Rapier Carrier shooting across up to six different enemy units, if you so choose).
Now, looking at the Thunderfire Shells, you have the following average damage output (when buffed by Azrael and a DA Lieutenant):
24D3 x Thunderfire Shell shots at 48″ range –
**Against GEQs – 22-23 dead models
**Against Ork Mobz – 27-28 dead models
**Against MEQs – 11-12 dead models
**Against T4 2W Primaris units – 5-6 dead models
**Against TEQs – 2-3 dead models
**Against Centurions – 1-2 dead models
Against Heavy Infantry, the Thunderfire Shells are vastly less efficient than the Shatter Shells, and even against lighter troops (like massed Conscripts or Cultists or Gaunts or Orks), they are better, but not overwhelmingly so. So, why even use them? Two reasons… one, range and, two, indirect fire… with a 48″ reach and the ability to fire at units completely out of line of sight, the Thunderfire Shells give you the ability to begin influencing the game Turn 1, tearing up all kinds of light-medium infantry and freeing up the battlefield for the remaining 1100 points of your army to maneuver in, seize objectives, charge your opponent’s Gunline, etc. etc. Also, with the ability to render an entire Ork Mob or Conscript blob combat ineffective (if not wiped out entirely) every shooting phase, you can undercut entire portions of your opponent’s strategy, especially if it hinges on board control, using cheap infantry hordes to “screen” his main forces or block deep-striking allies, etc.
Finally, beyond the firepower detailed above, with support from Azrael and the Dark Shroud, the Rapier Carriers are remarkably survivable for their points costs. Below is the average number of shots it would take to kill a single Rapier Carrier, given that it has a 4++ Invul and -1 to Hit, from some of the common weapons on the tabletop:
**BS4 Bolters – 72 shots/dead Rapier
**BS4 Heavy Bolters – 32 shots/dead Rapier
**BS4 Assault Cannons – 24 shots/dead Rapier
**BS4 Plasma Guns — 24 shots/dead Rapier
**BS4 Overcharged PG/Krak Missile – 12 shots/dead Rapier
**BS4 Lascannons – 6 shots/dead Rapier
Remember, all of the above shooting is what is required to kill a SINGLE Rapier Carrier, meaning that your opponent has to do this six times over to remove your entire Gunline…. in the meantime, you can continue to punish his forces with the rest of your shooting, seize critical objectives while he focuses on killing your Rapier Carriers, get your assault units stuck in, etc.