Having never seen more than 5 minutes of DotA in action (my only MOBA experience being a year of LoL), I find watching Dota 2 to be fascinating. I have gone from being indifferent towards Dota 2 to being ridiculously excited for its release.
@TotalEklypse: You might want to look into Red Orchestra 2. Not sure if it totally fits what you're looking for but judging from the original Red Orchestra it will probably be the best/one of the best games walking the line in terms of enhanced realism while keeping the tempo up.
Very cool news that this is being implemented in BF3. In BFBC2, "keeping heads down" with a squad automatic weapon more or less gave every enemy sniper something to shoot while giving little to no tangible benefits to balance the risk.