The -2 is a significant bonus for the squishy's defence and the damage from not attacking the paladin is significant.
You have to attack or be adjacent in order to maintain a mark.
I'm more cncerned about an Archer-Paladin once people can create their own characters. "I shot you from way...
I thought you rolled for each power seperately each turn.
AFAIK all powers recharge on a 6 with some also recharging on a 5 and a few more on 4/5/6 etc.
How often do you get Feats?
In the preview characters, both the Fighter and Paladin get to "mark" an enemy (giving it penalties for attacking others) but each enemy can only have one Mark at a time.