The best way to build an assault centric
CSM army is to use the Black Legion supplement. Here's a post about the lists I run and how they work:
http://www.dakkadakka.com/dakkaforum/posts/list/561108.page#6211910
I understand people's objections to the supplement and also how misunderstood it is. The bottom line is
CSMs suffer a lot due to a lack of mobility on the board. Having an uber
HQ who can take a ridiculous number of shots then dish on your opponent is a good way of reducing attacks against the rest of your army and getting them up the board. When you consider statistical averages, it would take more than 100 bolter shots to kill a
CL decked out this way. When I have played him, the chief source of wounds by far has been failed
DW rolls and he hasn't actually gone down in a game.
The assault version of my army uses Chosen with flamers to assault everything on the board. They take Rhinos, which are a little more survivable due to the
CL. I have taken
MoK and
MoS Chosen in this role and believe
MoS to be the better of the two.
The extra attacks with a
MoK unit lets a 10 man squad give about 2 extra wounds when they get the charge. They are striking
MEQ at the same initiative, however, and the loss of models tends to reduce the effectiveness of the unit quickly. In general, I get one good assault per unit, which isn't bad, but there's not much left of the unit afterwards.
The extra initiative with a
MoS unit means my guys take less wounds, and the IoE allows them to shrug off some of those wounds. This is important when you consider the real strength of the unit: 5 flamers. No one wants to charge a unit with 5 flamers for fear of what happens on Overwatch. While I haven't really thought about the math, the flamers seem to more than make up for the missing attack. More importantly,
MoS units are more survivable. They don't generally die in games so much as fail morale checks when they get down to 2 or 3 models, and I can usually count on them for a single assault plus a joint assault with another unit afterwards.
When I compare them to spawn / bikers / berzerkers / raptors / regular
CSMs, there's really no contest in terms of 'killiness' due to the flamers. Having 5 flamers on a unit just changes your opponent's tactics. The Chosen don't really get assaulted themselves so much as chase things that are moving away from the flamers. They force opponents into situations they don't want to be in, like when a bunch of their troops are suddenly massed in a single spot, or when their big blob is suddenly really close to the table edge. In either case, these situations are really good setups for
CL assaults.
These units benefit from fast attack and deep striking
cc units. I do pair them with bikers, terminators and raptors to tie up enemy units so the Chosen can get into range. I also pair them with laspreds and havocs with lascannons to shoot up things they are not good against. I avoid pairing them with Heldrakes,
DPs or anything else that does a similar job to what they are there to do. I have not tried them with fiends, vindicators, defilers, Daemon allies, etc, but do understand they could benefit from such pairings.