I guess one of the things that is kind of bugging me too is the apparent lack of some kind of saving throw or ability to avoid or negate being marked. I haven't been religiously following 4E updates as they come out, but this seems to be one of the only things in the game that happen automatically with no chance of failure.
SWSE has some kind of cover fire or something, so I can see how marking someone relates in that way. So, -2 to attacks if a fighter marks, ok. But even still, in there if you were giving cover fire, that's all you were doing. The way this is written, the fighter could be playing rock, paper, scissors with the wizard hanging back away from the fighter and just 'throwing' marks all over the battlefield.
And if a fighter is talented enough to mark others, it seems that there should be things out there likewise talented enough to avoid being marked or unmark themselves.
But if its going to cause something else like an AoO or something where the target gets attacked by someone else for not attacking the mark(er), it seems like there should be a Will save or something allowed or an attack made against the mark(ed) target's Reflex or Will. But it also seems like if the target can move or shift away from the fighter that doing so would end the mark if the target is just suddenly not there anymore and the fighter has no immediate way of harrying his mark.
Especially for the Paladin mark where damage is inflicted if the target ignores the mark. I thought pretty much everything had either an attack roll or the target gets a save for anything coming their way that inflicts damage, yet that doesn't seem to be the case for the mark. The Paladin mark is basically an attack. A conditional attack, but an attack just the same.
Maybe there will be an Athiest feat that lets someone ignore Divine marks from paladins and such! Or maybe something where divine characters are immune to divine marks.
Paladin: Face me or feel the wrath of my divine awesomeness!
Evil Wizard: Sorry, gods don't really exist, and by extension, neither does their divine awesomeness. **Drops a Fireball on the Paladin's allies**
Paladin: Face me or feel the wrath of my divine awesomeness!
BBEG Cleric: Silly Paladin (rabbit), divine awesomeness (Trix) is for kids! My god outranks yours, so, neener-neener-neener!
Fighter: Aha! I mark you.
BBEG Cleric: Ok. **Casts Harm on Fighter.**