Forward: I am a North American player who is currently residing in Hong Kong. I have a year's worth of experience in North American TF2 - through ESEA and #tf2.pug.na, #tf2mix.
Since I'm here, I planned on participating in some AsiaFortress events. So, I hopped into some of the AsiaFortress pug to see what was happening over here in this scene.
You really need Mumble. It's harder because this is the system that you guys over here are used to, and there's more possibility that there will be players who cannot speak English, but these pugs are quite literally shitfests. Perhaps even with Mumble they could still be shitfests because of teams or whatever, but at least a Mumble provides a sense of communication - at least someone will talk or try to talk. These are just TF2 Lobbies with an integrated picking system otherwise. I've heard that there are other pug groups active in AsiaFortress which do have Mumble as a "requirement," and you'll find that if you start having teams in Mumble for these pugs the quality will improve if but a little bit (because there will be tryhard players like me who like to comm even in pugs). The American pug systems all have Mumble usage and it's excellent for showing new players a glimpse of what being on a real team will be like. From what I gather, these pugs seem like the only way to get a first step into the community, and it's a terrible foot-breaking step the way it is now.
Just offering my thoughts, as both a newcomer to AsiaFortress and someone who has experienced a different continent's TF2.