I wrote a blog on blockers:
http://40kunorthodoxy.blogspot.com/2012/08/warhammer-40k-blockers.html
So my take on this is twofold.
First is this: Grenades. It simply IS tue that enemies can really hurt your pods with grenades and create a lot of
KP. So you are leaving yourself a little vulnerable in that mission unless you have a solid plan. For that kind of operation, i am surprised you favor tactical Marines but since you do, you're going to have to REALLY measure out those distances and make sure you give your men the chance to act after they drop.
Having said all that, the Drop pods provide cover and with a Priest around and the libby, its quite likely that that could really protect your troops pretty well. The Shrouding Power and Feel No Pain hiding behind pods? tough to kill.
This would work EXCEPTIONALLY well in the Relic mission. I myself have thrown my women into battle, sacrificing unit after unit to form walls the enemy simply cant move passed fast enough. It works. A pod army is kind of ideal for attempting that.
My only concern in doing it with Pods is that Pods can't be reimbarked. So whereas with a Rhino, I would disembark, thusly saturating the enemy with targets, and thus less total units die/are made combat ineffective than would have been the case. Then the remnants could get back in and they are now scoring, their rhinos still alive. This tactic is a time play but it works.
You dont have that flexibility with the Pods so you are going to have to make the pods themselves a concern to the enemy. If you do this I think it may mke sense to put Deathwind Launchers on them. Forces the issue of them trying to kill the pods rather than your men.
maybe you should show a list where you do that so we can look more closesly at it.
Also, the StormRaven while it is super cool, may or may not be overly necessary if you do this many pods.