Hi Sharkey,
It seems that some researchers believe that lekking also reduces aggression amongst bucks when the population density is high.
I own 120 acres of ancient woodland which adjoins 2000 acres of FC broadleaf woodland and during the rut there are probably 50+ bucks (all age groups) around. There are numerous scrapes throughout the woodland, some of which are close together but I think it would be almost impossible to find out if they are lekking or just holding stands without having 24 hour camera surveilance of the area. How else can you get close enough to them without them moving away?
One really interesting thing you mentioned which, although I have seen it so many times, I never realised before you said it, is that leks are typically 2/3 of a way up a hill. Well, lek or rutting stand, they all seem to be on the side of a hill, never on top of the hill and never low down but mostly over half way to the top. I can only assume this to be some kind of defense stategy, although what exactly I don't know. If it were purely to achieve a good aspect over the feeding area and does, then you'd think that the top of the hill would be better ???