So, I find myself taking a first whack at homebrewing a new class. Well, updating a 3rd party setting to 4e, and that requires a new class: the steamborg. A steampunk cyborg. Considering their iron toughness, defender seems an ideal role. So before I brew up a bunch of powers, I wanted to come up with the basic premise of how the class works. And I find myself pushing the boundaries of what it means to be a defender.
The role of a defender is to encourage enemies to attack the defender first - by punishing enemies for doing otherwise. Thus far, this has always meant a mark mechanic that allows the defender to get in an extra attack if enemies ignore the defender. But I wanted to break the mold a little here with the steamborg. Not greatly, but at least try out something new. The steamborg still marks enemies, and the steamborg still punishes enemies for ignoring that mark. But I'm redefining punishment. Within the DragonMech setting, steamborgs struggle with a mind no longer completely human, prone to bouts of becoming an unfeeling machine. I wanted to capture this with the mark. When you attack the steamborg's allies, you draw out his inner Terminator. In his... well, rage isn't quite the right word... he becomes an unstoppable killing machine. When you ignore his mark, he immediately gains temporary hit points and a bonus to damage rolls until the end of his next turn. I really like this form of discouragement: ignore this defender, and he becomes unstoppable - you better not ignore him. And the damage boost is there to give some offensive power to this defender.
For feats, I'm thinking one gives him a +1 bonus to attack rolls when the mark's effect is triggered, another grants him an instant saving throw (against only 1 effect) when the mark is triggered, and there's a utility power that lets him recover hit points when the mark is triggered. And this is warlord-style healing - just refusing to go down.
I think it's an interesting idea, and I'd like to explore it, but do you think it's balanceable? Being so different, it'll be harder to compare. In its favor is the fact that the mark's effect triggers with no action (and the steamborg places marks like the fighter - lasting until end of next turn, a no action effect applied to every attack). On the other hand, the effect isn't stackable, so a steamborg who has several enemies trigger the mark gets no benefit after the first one.