Roles don't prevent you from playing the game in different ways, they don't prevent you from playing whatever you want regardless of what the party may need to be well-rounded.
And it was harmless ribbing.
Then I will choose to take it as such.
I dont mind marks per-sae or "tanking mechanics" as such. Frankly, even you you were to use a "role-less" game (as I prefer) the fighter does stand out as the guy who can take the most and therefore the one who should put himself forward as a target.
The thing is I know my players. The guys who like playing fighters dont like playing tanks. In fact, when we started playing 4e, it wasnt the fighter players that played the tanks, it was actually the guy who traditionally played the rogue!
The guys who played fighter actually preferred to be fighters as damage dealers (and this was well before essentials Slayer came out). They arent power players, so hitting the boards to up fighter damage was never going to happen.
I guess I would say, sure, go for some tanking mechanic, but I wont buy into the debate as to which one. As a DM, the thing I want for my group is the option to not be tied to a tanking role as a fighter, and offer alternate options.
Yes. Roles have been there by proxy since the beggining, but within our group only me and one other even think like that. The others dont, and for their sakes, I would just prefer for the fighter to be what they want it to be, a role-less battlefield titan.