Legends & Lore is switching focus from the overall bigger picture to a weekly progress update, so we will see what that entails next week. Hopefully this includes flavor and crunch previews.
While we did not get the exploration rules in the latest packet--which, I was not aware we were supposed to get--Mearls states that they will be in the next one. The brief overview he does provide sounds similar to how it works in Dungeon World: when you are traveling, each character gets a job, either trailblazer, scout, or quartermaster. You then make a Wisdom check (roll+WIS), with success or failure affecting what happens during the trip.
The exploration rules in Next will provide more structure while exploring. Turns are a thing, and there will be sets of actions that characters can perform such as making a map, checking for traps, and watching for monsters. I remember having to actually draw out maps based on DM instructions in 2nd Edition, but I am curious as to how making a map will be handled, what benefits it will provide, and how this will all be abstracted (if need be). There are also guidelines for pace and random encounters. He mentions that they were handy when he ran Isle of Dread, so I will probably give that another shot when the next packet is released.
The few reactions I have seen towards the barbarian unanimously agree that it is a bigger, better fighter, which is why it looks like they are going to rein it in, while making the fighter more flexible.
My in-play observations are that most of the time it is just a bit tougher at the start (something like 2 hit points), and more straight-forward due to a lack of maneuvers. Reckless Attack has some situational use depending on a lot of factors, including the number, type, offensive/defensive capabilities, and position of enemies. Rage changes this up, making the barbarian much tougher, more accurate, with just a bit of extra damage output.
How much better, I think ultimately depends on how many encounters you throw at your party in a day. If they run into one random encounter each day while traveling well, then the barbarian is probably going to easily outshine the fighter. The same goes if they are freely exploring a dungeon with largely static threats and no time constraints; if they can come and go as they please, then there is little incentive to keep going when their rages run out.
In other words, it can create the same problem some groups have with clerics/wizards, per-day spells, and the 15-minute workday, except now there is a third class lobbying in their corner.
I have said before that I would prefer the barbarian to have some mechanic that lets her accumulate dice/tokens/points on a round-by-round basis, that let her deal bonus damage, shrug off damage, activate more supernatural powers (like 4th Edition barbarians). Couple this with terrain-based features from 4th Edition's berserker and I think you have a very solid, very unique class from the fighter.
As a final note, those massive battle rules sound pretty interesting. I have never run a war campaign, but getting to test new rules sounds like a great opportunity to try that out.