Hi, I've only just started on the HR5 monsters and I'm having a hard time figuring out when to capture them! Low Rank monsters always limp away when they've been hurt too badly, so you know you can capture them at that point. But the High Rank monsters, they take ages to start limping even though you'd be able to capture them at that point. I was just fighting a Rathalos for 45 min (yes, I'm not very good :P) without him limping even once when I thought I'd just try and see if I can capture him and it worked! Honestly, is there some other indication of when the capture point other than getting the right armor skill? By the way, I'm playing solo since my PSP can't connect to the router so I'm not sure if there's a difference in multiplayer. :S
High rank monsters will limp if you give them the chance, but it probably won't happen if you're playing with multiple people and beating the living daylights out of them. The only real way to tell is, like you said, to have the armor skill.
However, once you fight enough monsters you will gain an ability to just tell if a monster is ready to cap based on how long you've been fighting and how long it's taken you to kill/cap the monster in the past. My friends and I are all pretty good at determining if a monster is cappable or not from having fought so many things.
PSN-Ponmbr Victim language is when you explain it as if it's someone else's fault that you're stupid.