I think it's probably stretching it to say the Guard never uses drop pods, as it's a large and varied institution. In all honesty, I suspect Naval hardware support for drop pod assaults is actually more wide-spread than the Guard training and doctrine for their use.
The latter is precisely why I don't think the Navy would sport such equipment. Surely, there is some variation throughout the Imperium when it comes to ship classes, but I would not expect this to extend to something as basic as "drop pods y/n" - and I cannot think of why the Navy would build an entire class of ships just on the slim chance that some day far in the future they get to use them if it's not a standard tactic (which it does not seem to be, from all I've read about planetary invasions so far).
As for Epic … phew, that's getting tricky. I know that some editions of that game are even older than 2E of 40k's main game, and a lot of stuff has changed in there. At the same time, I wouldn't want to discount the possibility.
Since this is 40k and we don't actually have a true canon anyways, I'd thus propose to go with what you think fits best to your personal interpretation of the 'verse.
Well, drop pods are available as a ship component in RT… I doubt many Rogue Traders have space marines to fill them.
Rogue Traders seem prone to do a lot of customisation - this includes fitting their ship with equipment that the Navy or the Guard would never use, because it is deemed inefficient or a waste of resources. In case of drop pods, it could be because the Rogue Trader in question thinks this is a good strategy, regardless of whether this is actually the case or how practical this is. Normally, the users of drop pods seem to wear power armour, which would surely take a lot of shock out of the harsh landing. If the RT doesn't manage to equip his entire landing force with power armour, he may well have to find alternatives (shock dampening gravity fields?), harder troops (Ogryns may not mind), or simply shrug off the potential casualties.
IF that is how one interprets the stress of a drop, anyways.
If the IG dumbly flew wave after wave of landing craft at massed AA batteries, the Imperium would not have lasted 10,000 years.
That's why the IG/Navy does not (usually) practice such landings and either bombards the hell out of these batteries or deploys in sufficient distance and then has ground troops advance in a traditional way. If you want to get straight into the heat … that's exactly what the Space Marines are meant for. All a matter of specialisation.
Reading the Gaunt's Ghosts series I note that Blood Pact forces use drop pods. Is the Archenemy employing more sophisticated tactics than the IG?
This might simply be a question of an individual author having his own idea how the setting works. It doesn't quite fit with the Blood Pact article published in WD #292. At the same time, Chaos warships aren't standard Navy models anyways, so all bets are off on that topic.