Personally I think DS2 was one of those rare situations where the sequel was a significant upgrade in every way, though I may just have less-than-fond memories of the original tainting my analysis of that. Still, I enjoyed the original enough that when a friend told me there was a sequel I snapped it up.
The first one was kind of nuts hard, but this one isn't all that bad. I've only *had* to stop and grind once (for the boss of Day 4), although I did wind up overleveling for an optional fight at the start of Day 3 (I think?) because I grossly overestimated how dangerous it was.
My only real beef is that fusioning up demons is still a pain. You have to combine lower level demons to get midlevel demons to get higher level demons, repeat in a few levels. The compendium (which allows you to register a demon type and resummon it for a rather significant fee - at least, I think that's how it works) does help but that also requires some Macca grinding.
In general I like the story and characters much better, and it seems like there's tons more Physical skills so my preferred main character build is a beast.
Part of why everything seems so easy may be that I've been focusing level up stats into Strength and Vitality, keeping the MC equipped with Mow Down, Berserk, and usually the best healing skill available (with just enough Magic to equip it). Then his monsters are a Kishin (their racial skill allows you to make two skirmishes in a round) and a Beast (Animal Leg lets you move after a skirmish). If the enemies are set up right, you can move up to 12 squares each turn - and very little survives two poundings from an all-physical team, even if they're tank types.
The friend I mentioned early has an MC that's Strength and Agility, which when combined with the Multihit skill apparently gets even
more insane, but I enjoy the absurd survivability that a high Vitality gives me (let the monsters gang up on the MC, who doesn't even care, then bring in all the other characters to finish them off). There's actually an Auto skill called Battle Aura that negates weaker hits which not only keeps the whole MC's whole team from taking a significant amount of the damage thrown at them, but lets the poor slow bastards get extra turns, too! (It counts as the enemy hitting a strong resistance, apparently).
You can probably tell I love turn based strategy games with mix-and-match systems like these, heh.
Also, I debated putting this response to the OP's spoiler in a spoiler, but since I'm not naming names and it's kind of a central gameplay thing: Letting party members die (in the story, obviously) has the potential to come back and bite you since the game semi-frequently restricts who you can add to your party. I've only had one (sort-of-optional) mission where this would have actually affected anything, but I wouldn't be surprised if there are more later.
I suspect that some characters dying may also limit the time-spending/bond-forming options with certain other characters, but I'm not entirely sure of this.
That said;
Jungo and Keita aren't very good characters, stat-wise, at least in my opinion, so you certainly aren't missing much.