I think the reason the film didn't focus on the other pilots was for dramatic efficiency, in that when you have a film with pretty simply drawn characters, you can't afford to throw too many of them at the audience... because then they become cannon fodder and the audience will start thinking about the nature of the conflict, and you don't want the audience doing that - asking 'why?'. The experience of watching the film has to be about the pilots interfacing with the machine, and not knowing if they can pull it off, that was the motif in every scene. You know the chinese pilots are cool and have their moves down, same with the russians. Those things are static, and don't add tension. That's precisely why you kill them off immediately, because it forces the audience to root for the main characters... whether they want to or not.
(Like in Titanic, you're hopes are high when you're going in thinking about what the story will be about, then words start coming out of the main character's mouths and you realize you're going to be stuck with them for 3 hours and your face kinda goes slack..)
My biggest beef with Pacific Rim was why the Australian son couldn't eject to safety before the nuke went off.. his father wanted the colonel to take care of him (THATS MY SON!), and the 2 leads eject to safety, from another dimension, in the middle of a firefight, so why couldnt the son eject?
Also I don't know why Idris Elba yelled his inspirational speech about cancelling doomsday , etc.. you yell when there's like hundreds of troops and you don't have a bullhorn and you want to make sure you're heard, but the facility only seemed like it had a few dozen people, and they were all right there. Elba is good at subtlety, but they had him barking in this film, I didn't think it played to his strengths.
Mostly though, I was happy that Pacific Rim succeeded as well as it did. I hope it gets a sequel, because I totally want to see them make a yaeger that combines into a giant one, ala Voltron/Gathchaman..