Destiny is currently offline for a bit, as Bungie rolls out a patch that fixes a number of little problems with House of Wolves. It also increases the drop rate for treasure keys, which should make your Prison of Elders farming runs far more fruitful.
In addition, the first bounty you complete each week nets you a guaranteed key. You'll also get more of them from ether chests.
The patch also tweaks some issues with bounties, Trials of Osiris emblems not going to the Postmaster properly, and a fusion rifle fix that now properly reflects rebalancing. For those with ammo consumables flooding the inventory, those stacks are now 100 high, so you should be able to free up some space.
Finally, if you don't have House of Wolves (and therefore cannot take missions from Petra), you won't be taunted by the mission icon over her head. You can read the entire patch notes on the Destiny website. You can also read our impressions of the latest expansion.
I've yet to dive back into Destiny for House of Wolves, but I've been watching friends tweet about a couple of issues this fixes. Editor-in-chief Andy McNamara was lamenting both a dearth of treasure keys and an overabundance of ammo consumables, which can't be discarded. Hopefully this helps him and others get back on track.