I think the link modifier was never intended for play, it was more of an admin tool.
As for dense ores, if this didn't change, it spawns every single ores, even the ones disabled in the configs.
At least, it used to do that, and you ended with 5 types of tin and copper.
What I meant by the dense ores is that in the previous version of Mystcraft you got larger veins of non-vanilla ores as well as vanilla ones, or at least they "spawned" much closer together. I read elsewhere on this forum that in the latest version the dense ores only applies to the vanilla ores and the non-vanilla ore gen is exactly the same as it would be in a normal world unless the mod authors have added their ores to the dense ore ore gen file/config. Is that still true and have any mod authors added their ores?
Re the link modifier, so is there now no way to teleport in the same dimension with Mystcraft? That sucks if so. I really miss my 'following' linking book that I always had with me to teleport back to my base.