You seem to be missing the point. Not about saying welcome. Just about being a community. Mumble detracts (as would any alternative) as not everyone has it, especially not new visitors. Instantly you have split the people on the server, those that have it and those that don't. Use ingame is the best solution to that. It's not about verbally welcoming people but about them being able to see / hear there is a community that they can then choose to join in with.
Another idea is that we regularly check the player logs for pol who have been playing on the servers for a while and send them a steam group invite.
yeah that was my point also, people are fickle & they want stuff handed to them on a plate usually, whether we agree on it or not thats just the way it is
For instance take the UT3 side of things
We run 3 custom map fun nights a week which we advertise weekly on various different forums, we take onboard map requests & suggestions and are constantly changing stuff around to suit people, we provide beta testing and feedback on maps and mods, we provide complete server map downloads updated constantly
The server is set up with multi votable options in relation to gametypes & mods which is constantly monitored & changed, we constantly strike to make game fair & fun for everyone by adjusting the teams (this imo is very important as it only takes 1 game where a player was on the wrong side of a pwning for them to never come back)
We run an open teamspeak and spam the ip constantly, we get all sorts of folk on there & they come back because its fun
Thats only part of what we do tbh