The Siege of Mersadie Hive was a custom scenario lovingly crafted by Arthur. As such, unless your GM is planning to borrow the scenario by hacking together what they hear on this episode and the notes on Arthur's blog, there's really no spoilers to worry about.
As always, be aware that the podcast is not really family-friendly, and features some background noise, if that sort of thing bothers you.
There's some (I think) very interesting discussion around the 20 minute mark of the interplay between balance, genre and expectations. Dan brings things out pretty clearly with the point that "the sorts of things that player characters are encouraged to do are the sorts of things which you probably wouldn't do if you had a 50% chance of dying doing it". Fate Points do tip the balance in favour of heroics, but there's a constant tension between wanting feats of heroism and the actual chance of getting away with it. The canon isn't a huge help here, because depiction of PC-level characters and/or Space Marines varies between portraying them as elite soldiers who are still very mortal, or as godlike warriors who shrug off the strongest attacks.
During the discussion my old favourite topic of problems with Assault Marines comes up again. In my defence, we recorded this long before I wrote a lot of my posts on this topic, because of backlog. I'll let the discussion stand for itself. We also discuss the Rocket Tag situations that more powerful enemies cause due to subtractive armour and so on. Arthur raises interesting counterpoints with discussions of the layers of death-proofing offered by RPGs versus tabletop.
This mini-campaign was a challenging idea, because in principle a siege offers a good sandbox, but actually it departs enough from the usual mission-based game that it puts extra weight on the GM. While there was a bit of work we could come up with, and we could probably have devised more if necessary, the onus is definitely on Arthur here to provide a steady and varied stream of things to deal with. Thankfully, I think he did a decent job of it, and picked a good time to bring things to a close. As (I think?) ended up being mentioned in one episode, I'm considering running at least one game set in the siege. It seems a nice rich environment to flesh out.
I wrote the above paragraph (like a lot of the show notes) while doing the editing, i.e. before I moved to the other side of the planet from the rest of the gang. While I'm still working on that Arbites game, it's probably going to be a while.
I'm really sad that we don't have recordings of the middle session, because this showcased the more active part of our activities: sending a recruiting and diplomatic mission to the Underhive to secure it from the orks, and sending the scouts on raids. We all take a lot of pride in the exploits of our boys, and they definitely done good. What remains in the recordings is relatively passive. Admittedly, this is different from many scenarios (in many games), which often feature pretty static plots for the PCs to interact with, so it's still hopefully a bit of a change of pace. However, we lost the section that best highlights how even an apparently passive situation, like a siege where the initiative lies with the attackers, can still offer opportunities for taking an active role.
It strikes me this would be a reasonable place to focus some effort - I know Deathwatch is aimed at special forces-type missions, but actually I imagine it's pretty common to use it for general Space Marine stuff, and larger-scale battles are a key part of that. Some missions designed for integration into wars might be a decent supplement. Siege-breaking, taking out supply chains or leaders, holding strongpoints, they're all good for heroics.
So that's it for Mersadie Hive. Hope you enjoyed this series as much as I enjoyed playing them, and indeed listening back to them as I edited. Do leave any comments you might have.