So far I've managed to make it through all of the books I've started, but Emperor's Mercy I only just barely made it through. By the time I got to about a quarter of the way through I'm thinking, "Where the hell are the Blood Gorgons? Isn't this series supposed to be about them?" Then a lone Blood Gorgon shows up for a few pages,so I keep going figuring maybe it was just a really long exposition. Half-way through I'm getting kind of annoyed, but there have been a couple of skirmishes that tease the idea that maybe some big fight is coming soon, so I keep going. Then the final climatic battle happens and it's difficult to keep track of what's happening. Almost seems like two or more authors are writing, because when the action is on the main character inquisitor, it's not too difficult to track, but when it skips over to following someone else, it seems like a jumbled mess.
Normally I'm someone who likes to binge. If I start on a series, like say the Blood Angels series, I will read all of the books in the series in a series. With the Bastion Wars series, it was all I could do to finish the first book, there was no way I'd have the kind of mental discipline left to finish the second if it was anything like the first.
I also came close to not finishing Sons of Dorn, but probably only because I had just so recently read the Space Wolf series, and let's face it, Sons of Dorn is essentially the first Space Wolf book only with the Imperial Fists instead of Space Wolves. Huge chunks of the two books are basically identical.
There was also some absolutely horrid novella about Lysander in the Architect of Fate space marine battles collection. You couldn't follow the action, the plot skipped around all over the place, former tech priests and tech marines becoming part of the ship's machine spirit, which seems to be a self-aware AI. I'm far from a purist regarding lore and all that, but that novella was a mess in so many different ways, I think it's fair to say even the author didn't finish it, let alone the editor.