As it is right now, for tank builds, between Fast Metabolism and Doctor, you can almost always justify taking Fast Metabolism but can hardly justify taking Doctor since it falls too much in the 'Quality of Life' category.
My recommendation: Make Doctor reduce the cooldown of medication for 1 or 2 turns, and give it a specialization that further reduces the cooldown of medications for 0,5 per Spec point.
That way Doctor stops being considered QoL and actually be a good feat to take