Yeah, marking needs some cost or risk to counterbalance it.
I'd give the target creature advantage on all attack rolls against you for as long as your mark lasts. This also reflects one of the effects of the 4E mark; it gives an incentive for the victim to attack their harasser. This may be imbalanced against the barbarian's Reckless Attack, though; maybe a flat bonus would be better. I am not sure.
I'd give the target creature advantage on all attack rolls against you for as long as your mark lasts. This also reflects one of the effects of the 4E mark; it gives an incentive for the victim to attack their harasser. This may be imbalanced against the barbarian's Reckless Attack, though; maybe a flat bonus would be better. I am not sure.