Yeah... I actually find 343's expanded lore to be some of the best content for the entire series. Broken Circle, Hunters in the Dark, Retribution, just to name a few fantastic books that I had a hard time putting down. And the great thing about it is how (except for Halo 5), you can pretty much ignore a large portion of the expanded lore and still understand and enjoy the games, which makes the series accessible to more casual fans.
They're not really doing a good job at creating or explaining the current lore, so none.How so? Under Bungie we didn't know the as much as we now. We have the forerunner novels, the book Broken Circle talking on the early days of the Covenant's existence, the Warfleet book, Halo: Mythos, Halo:Fractures. When it comes to expanded lore would say we are doing better with 343 over Bungie.
All of which I find needlessly convoluted or do a great job at ruining the mystery of the series. Halo was best when it was military science fiction with just a hint of something bigger with the Forerunners and the mystery surrounding them.
Now? Everything is explained, and explained poorly. The Flood? They worked better before their origin became 'magic space dust', or that there was an ancient Human empire that fought the Forerunners, which are now just sloth faced morons with delusions of grandeur. Not to mention ALL of Human achievement being reduced to nothing by way of 'genesongs' and other such nonsense. Oh, and let's not forget the utter character murder that they did to Dr. Halsey by making her 'Worse than Hitler', or how they just let a high ranking Elite wander around a military base without escort because they think he's 'harmless'.
Oh, and let's not forget the utter train wreck that Halo 5's campaign is. OH CORTANA IS BACK GUYS BUT SHE'S EVIL NOW ROBOT REBELLION LOL WHAT A TWIST
What about the big game ending event that was supposed to end the Flood threat? Oh no no, High Charity only partly blew up despite it being explicitly stated that it was going to explode. IT was even shown exploding. But no no, most of it is intact and some idiot Brutes just opened it up because the ONE single interesting thing 343i has done, The Banished, is too complex and actually interesting that they have to retcon what the player did in Halo 3 because they don't know how to write compelling antagonist factions. Oh, and let's not forget about hyping up Atriox only to give him a grand total of five minutes of screen time, and killing off their previous baddie in the first twenty minutes of Halo 5.
The story was better and more cohesive when Nylund and Staten were at the helm for the books and the games. They knew what worked and what didn't. They knew the exact amount of information to give the reader without destroying the since of awe and wonder that the more extravagant. The weirdest thing they ever did was the Slipstream battle over Reach in First Strike and the Sentinel factory on Onyx. What we have now? Now we have nothing more than your bog-standard amateur science fiction that explains too much, leaves too little to the reader's imagination and reeks of people who have no idea what they're doing and making all these crazy, far-fetched things up as they go along without any sort of regard to what came before in the hopes of dragging out interest just a little bit more. Sure it may look better than the self-published garbage you find on Amazon, but content wise it really isn't all that different.
I only hope that one day that Staten comes back and takes over the reins for Halo once again. It's a long shot, but the series desperately needs people that know what the series is and isn't. It needs a good EU nuking like Star Wars was given and reset it. Halo, Halo 2, 3, ODST, Reach as the core games, the Nylund trilogy and Contact Harvest as the books. Start over from there and build it out the right way instead of desperately trying to farm the franchise by hiring subpar writers or writers that push their politics into the universe.
Make it quality military science fiction with a hint of something bigger, not some Amazon self-publishing hack job.