Barbaric Cleave, Building Frenzy, Slayer, and Unstoppable have all remained unaltered. Strongheart has been fundamentally changed in concept; whereas before it granted free saves after hitting with an attack, now it boosts your recovery die up to a d12 and the adventurer feat grants you another recovery. This helps with the Barbarian's durability, but it's still a class with low base AC and its HP factor is merely average (unlike D&D 4E, where it was equal to the Fighter or Paladin in HP, or 3.x, where it had more HP). So despite the boost, it's still not the "tough guy" striker that it has been in the past.
The biggest change has been with Whirlwind. Before when you were engaged with multiple enemies, you could attack all of them and deal half damage. Now you make an attack at full damage vs all enemies, and take a hefty defense penalty. It emulates the flavor of big, reckless swings really well, though since the Barbarian already has extremely low AC you'll almost be auto-hit by enemies.
The Whirlwind change is interesting because while the Barbarian definitely still needs some work (I feel like it's still underpowered), at least it potentially has a unique niche now. Let's compare the classes that were traditionally (to use a 4E term) strikers.
- Barbarian: With Whirlwind, it's a glass cannon AoE monster. Again, I'd advocate that it needs a defense boost; after all, Monks in 4E could get killed pretty easily and they actually had great defenses. Putting yourself in the thick of things to maximize your offense is simply dangerous. As written, using Whirlwind to maximum effect is pretty much suicidal (the caveat being that I haven't seen the Barbarian in play). Barbaric Cleave gives him more multi-attack potential, further reinforcing the theme. Rage gives him impressive spike damage for an encounter as well, and as a class feature all Barbarians get it. Slayer and/or Building Frenzy are good ways to situationally add damage dice to your attacks, meaning that unlike most traditional AoE specialists the Barbarian hits multiple targets hard. Who knows, maybe a well-built Barbarian does have enough offensive punch to keep up with the Ranger and Rogue, but I still see them as the class that's most easily killed, and you don't deal any damage when you're dead.
- Ranger: This guy's the versatile striker, but virtually all builds will emphasize multi-attacking to some extent (whether that's via two-weapon fighting, ranged attacks, or by having an animal companion that can attack). He has the best defenses of the bunch, but also the fewest defensive "tricks" to mitigate damage (unless you count the animal companion's damage-soaking ability). Ultimately, the flexibility to lay two attacks on the same target or to attack two different targets is useful, though most significant is arguably the ability to get a "second chance" to hit if you roll a natural even (or have an animal companion), making the Ranger highly accurate. The class also has several versions of "situational improved criticals," and the spell-dabbling just makes it all the more flexible. While he's probably not the damage monster he was in 4E, his versatility and well-roundedness better represent the self-sufficient woodsman that he typically represents.
- Rogue: The Rogue is a bit swingy, and specializes in single high damage attacks. Again with the caveat that I haven't really played the game yet, he's probably the class with the highest damage potential. His numerical defenses are really low, but with the momentum mechanics he'll have plenty of opportunities to mitigate damage, and his powers very much support a highly mobile "skirmisher" playstyle so he'll probably be safe from attacks a lot (or at least open up enemies to being intercepted if they do go for him). From a meta-game perspective, he's also the most complex striker in-play, unlike the relatively simple Barbarian and Ranger.