Yeah, the problem really "just" rests with combat-focused characters - such as the Renegade - trying to get a bit of spotlight, too. Human characters in general can find a role either behind the scenes or by utilising knowledge and interaction Skills, but I'd recommend discouraging players from picking the Renegade once you have CSM in your group. (or removing the inflated gap between "Legion" and everyone elses weapons/armour)
Unless they're fine taking the back seat, that is. The Archetype can still have interesting concepts, such as a skilled assassin for infiltration and targeted violence, or even a pilot/driver kind of character.
Exactly. Renegades are very, very useful - but if a player wants to stand in line between chaos marines trading bolter volleys, he'll be disappointed.
Assassins? Excellent. Adroit ajility and not wearing bloody powered armour makes them the first choice for getting places that heretics should not be.
Commanders? Equally good. Adroit Fellowship, along with Excessive Wealth and an infamy bonus, makes the requisition stage funny. A conversation from the last game we had:
"And the Iron Warrior?"
"Some sort of transport ship." [Rolls]
"...Fine. It won't be combat-capable, though. Yup, okay, the Night Lord?"
"More stalker bolts." [Rolls]
"Okay - one reload for each pistol. Thousand Son?"
"What do I need for the ritual again?"
"Mostly just you. We'll call the assorted other components a single...Very Rare? That sound fair?" [Rolls]
"It would be if I could roll anything less than a ninety."
"Tough. Improvise. Stigmartus commander?"
"A reinforced battalion of veteran Stigmartus Infantry."
"You can't....no...no, you probably can, can't you." [Rolls]
"Yes, apparently you can. I take it the covert approach plan is being rejected?"