You have to hand it to Lab Zero, even though Skullgirls released back in 2013 they have not stopped releasing content updates and balance changes. As you can probably guess from the title alone, today's Second Encore+ update is a combination of both. It has brought in a ton of balance changes to a variety of characters, further improvements to the tutorial and training mode, a new lobby system, as well as a whole bunch of other changes, additions, and bug fixes.
I would love to give you a summary, but the patch notes are so ridiculously large we would probably be stuck here until tomorrow night. So if you're interested in all of the details you can find the full, extremely detailed patch notes over at the official website. And if you're just looking for the balance changes you will find them near the bottom of the list.
On a slight side note, as someone that isn't really a fan of fighting games I have to commend the developers for their continued work on the training mode. Even though I have barely any experience with fighting games I've been able to pick up some of the more nuanced techniques with surprising ease, so to see the team release even further improvements to the training mode is a great thing indeed. If you're a new player you're most likely going to get your ass kicked in online play regardless, but at the very least Skullgirls gives you the means and the knowledge to fight back.
And speaking of new players, if you haven't check out Skullgirls but feel like adding a new fighting game to your repertoire, you can head on over to Steam to learn more.