A few things...
First, on the final fight in general, the thing I'll emphasize is how much fun I had with it. We were first level characters. The DM threw a horde of kobolds at us. We ended up dying. But in the process we had all sorts of interesting abilities to use and decisions to make. As I said, I had a chance to use every ability I possessed in that final fight (including two of my skills). I was channeling divinity, breathing lightning, laying on hands, calling on my daily and encounter powers - it FELT like 300, with a mighty struggle against overwhelming forces. Meanwhile the kobolds themselves were using their "shifty" power, which lets them shift as a minor action, so they were swarming around us, striking wiith the flank and then shifting away to let another kobold step in for the flank; when two of us finally managed to get back to back, it was a big deal! Their leader was striking with mighty blows that could hit two of us at a time. Just as we had all of our powers we were calling upon, the bad guys had their own tricks. One of the things I like is that if we'd been fighting hobgoblins, the battle would have been completely different, because that shifty ability is a kobold thing. When you're dealing with kobolds, you need to be ready for that constantly moving force, and for the likelihood of lots of flanking; goblins, hobgoblins, and orcs all have their own racial abilities that will color a battle against them.
Second, on the paladin's mark. It's not my place to reveal rules that haven't been revealed. However, I think that I can say that while the mark has changed, the fundamental concept of it - fight the paladin or take radiant damage - has not. The changes that have been made prevent some of the sillier situations seen before, where the paladin can mark someone and then runs away. Without getting into specifics,, the way I see the power is this. The paladin calls out the creature and says "These people are under my protection, villain. Face me, or feel the warth of the Silver Flame!" If the opponent meets the challenge, that's fine; the paladin is a divine champion, and the powers that he possesses have been granted to him to fight this battle. If the creature scoffs at the paladin and refuses to face him, he is scoffing at the paladin's gods - and then you get that radiant damage. It's not the paladin blasting the creature, it's the force that empowers him; the gods themselves are backing up the paladin's challenge. "Show courage and face our champion - or face our wrath." But the paladin himself has to back up the challenge. If he makes the challenge and then runs away - denying the enemy the CHANCE to fight him - the enemy won't be punished for ignoring him. So in my case, I was never in a position where the marked enemy lacked the ability to fight me. They could have chosen to ignore the mark and taken the damage. But especially as most of them were fairly weak creatures, they generallly chose to answer my challenge.
