My choice at the moment in guild is to either only take the best players to EC/TFB HM and thus alienate my other raiders or take less well played raiders and accept the fact that we're gonna wipe all night and waste everybodies time. I'm in a lose/lose position at the moment because there doesn't exist a raid in which to train well-geared-but-under-experieced raiders.
Lost Island HM is a nice place to start, it has many mechanics that are similar to EC. I think you need to accept the fact that not all players are dedicated enough or capable of EC/TFB HMs. I think most can learn, but there has to be a will. I understand it must be hard for a raid leader to leave people behind either because of gear or skill.
In my guild we have two players pools, Progression and Casual/Social with different requirements. People apply for a team and can switch if they want to be more hard core or relaxed. So far it works great for us and people understand that there must be requirements or else it will affect everyone. You probably do this already, but maybe be a bit stricter? hehe
Just trying to be helpful here