He's right about intersections. It is illegal for taxis to stop too close to intersections so lots of drivers won't risk it, especially at particularly busy intersections.
The thing about groups of people is that when people are all standing in a cluster waiting for a taxi, inevitably some will break away and move and try to move a bit ahead of the crowd so the coming taxis will get there first. Then others in the crowd will try and move ahead of that crowd. Eventually you end up walking halfway down the road trying to be at the front of the taxi crowd. What we've actually done when we're in a busy area where it is hard to hail a cab is get on a random bus and ride it a stop or two down the line to where the crowd has thinned out a bit and there is less taxi competition.
There is very little in China that ticks me off more than people outright stealing your taxis out from under your nose. You know, when you've been waiting somewhere for like 15 minutes, a cab rolls up and out of nowhere some other dude just jumps in and grabs it. This is like queue jumping, but worse, because you have no idea when or if another taxi will arrive, or if the next one will get stolen too, and once the taxi stealer has jumped into the taxi he's gone and you can't do anything about it.