No.
I don't mean no to the awareness for tanks. I mean no on the second part. Any classes efficiency goes up the more situationally aware the player behind it is. Hardly any difference between how "difficult" it is to be aware on a dps, on a healer or on a tank, so don't spew this nonsense around.
Edit: As to what madtycoon said about skill cap and tanks I disagree about as much as I disagree with theronfett. It is not just a tanks job to peel, a dps and a healer has to be just as aware of his/her surroundings in order to use the kit he has at his/her disposal in order to save his team mates, be them offheals, kb, soft cc, hard cc, long cc, roots, pulls etc (not to mention that you have to be awake for offensive cc as well, not just defensive). Not to say that it's difficult, this game does not have by any stretch of the imagination a high skill roof, but that is another matter.