A recent comment on one of my vanguard mini posts got me thinking more about how I use my assault and vanguard marines. Currently I have 2 10 man squads of jump pack assault marines. These units each have a sergeant with a weapon upgrade and 2 special weapons with a power weapon sergeant with 2 flamers for horde control and a powerfist sergeant with 2 plasma pistols for MEQ-MC duty. These units usually only are fielded together as part of my battle company in Apoc games. I also have 2 10 man squads to Vanguard marines which ride to battle in Rhinos. These units have a whole range of upgrades available but I generally only upgrade 3-4 of the marines each differently. My minimum upgrades are Relic Blade Sergeant, Powerfist, Lightening Claw. I then add a meltabomb followed by a power weapon if points are available.
Does Heroic Intervention make up for this gap? They did a nice job making a very ironclad special rule covering almost every exploit possible. You have to declare you are trying it before rolling scatter dice, you cannot have a character(so no gate of infinite Librarians moving you around), if you declare you cannot run(no fleeting from Shrike) or shoot even if you end up outside assault range. This will leave you as blast bait if you miss distance for the assault. Since you have to end up within 6 inches of the opponent(hopefully a high value target), you are having to deepstrike close probably into a densely occupied region. This means you probably need to get a hit on the scatter die to get the assault off or avoid the mishap table. Assuming you are not cheating with your dice rolling this makes this process very risky. You can diminish the risk by using locator beacons on drop pods or scout bikes to guide the unit in. The problem here is that you opponent will always get at least a turn to respond to your placement of these before the vanguard arrive. They can either destroy the beacon unit or simply back up a few inches to be more than 13-14 inches from the beacon. Another problem is that drop pods are fixed in their location so if you vanguard are a little late they might not have anyone nearby anyway. With Bikes, if you turboboost them close to the target and the vanguard are late you have essentially wasted a turn of action for the bikes and placed them right into the opponents sights.
Now we will consider Rhino based units ignoring drop pods since I do not see the point of putting an assault squad into a pod. I see giving up the jump pack movement for the drop pod assault and inertial guidence only as not worth it. Maybe on a crowded Apoc or cityfight board. If we again start with 10 marines and fist in a rhino, the veterans are about 26% more expensive but have almost the same gain in hitting power (21% MEQ, 27% Ork). So the unit is essentially starting in the money without the extra upgrades. You might say you would like higher effectiveness difference than cost difference to account for the fewer overall wounds the army has to give. This loss is probably balanced by the fact the combat effectiveness difference is higher when the vanguard recieve the charge or the combat lasts beyond the initial assault.