I started tanking just a bit ago when I returned to the game this month after a 4 month hiatus. I primarily am Bard/ Healer but I still appreciate tanks to mark. The enmity I generate as a bard is way higher than you expect from your math. For practice when a tank does not mark now (I assume cause they don't have it in their hot bars for some reason) I start marking for them cause it helps everyone and communication is key in this game! :-)