there is no minimum requirement regarding runes for raiding
most players have minimum runes level 5 and better
some guild make their "own rules" regarding runes & gear for raiding but thats another story
the game is doing fine
there will very soon be the next big patch (version 6) that brings the new max level 65 and a "gearreset"
there are players everywhere, but in the endgame-zones are more than in the leveling areas of course
(but with patch 6 where new race "priden" comes there will be a new startng zone and it will most likely be very crowded)
there is another thread which is maybe intersting to read for you, Groot already linked it above my post