Do not forget, that BA is also SM, so they are basically expensive. A combo with a DC+Furioso, Landing Craft LR Redemers will be super expensive -and I don't mention the Sanguinary Guard+Supreme Commander unit.. Maybe worth more, than your target formation, even more than a Reaver (At least 2-3 activations vs 1 target, not mentioning the possibly lower starting activation number of a SM army). It means a big part of your army will sit in the middle of the enemy, just after they overkilled a single enemy unit.
Against an army, like IG, it means you're dead, because the high number of Sustained Fire capable long range units (Assault Marines have a single 4+ save, SG have a single 3+! Vulnerable to MW artillery, FF MW weapons, etc..). Don't stop the thinking at the moment, when your units arrive to the field -think over their next actions -will there be any? Or they will commit suicide with an assault like that
Don't forget. that they have no AP/At ranged weapons! Once they reached their target, they will stuck in the middle of an army, with 5+ FF, without ranged weapons. Sound scary to me
Assaults need to be prepared -this is the hardest question in a BA army. No real long range firepower, no Warhound Titans to soften target formations, etc! I think nerfing the Stormraven to 2x one shot is making assault preparations insanely hard against RA armies- AMTL, Nids, Stompa mobs, Leman Russes, IG Super heavies, etc.. Next to the even poorer AT capabilities to the list.
Assault Marines usually never reach their target, if they go without transport! Their are the primary target of a smart opponent, who has the firepower on his side. I think buying CH to them is a waste of points -they will be an even higher priority target
The only reason to buy a Captain is to involve previously dropped units to fight! You already mentioned the drop-light army lists weakness, the limited transport capacity of the Strike Cruiser.
So, my opinion is to leave the Stormravens to 4 one shot, which looks fine ,especially next to the owerwatching scout long range, non-transport Vultures!
