After reading the first 5 pages of the post, I have decided to reply with some of my own opinion:
When I first started as a newbie, I join a party full of newbie NA player. Being a RDM in the party that has a WHM, I am being ask to focus on healing...
On my next party, I was being invited into a party that already has a WHM and a BLM. After having the lesson on my first party, I sit back and doing purely mage job. Then the JP BLM (rank 7 at that time) and the WHM start to tell me that I should have meleed, and the BLM go so far and telling me (he can speak fluent english) a non-melee RDM is no good since he does not fully utilize his talent.
Since then, I have been meleeing in most of my party and really enjoys it. Most party do not mind that I melee, as long as I am doing my mage job correctly, namely enfeebling, backup cure, enhence, dispel, and later on refresh.
Lately, my static party ask me to try out what happens if I just purely act as a mage and not to melee, because they felt that it might help the XP comes in faster (we got into a long discussion after a dead tourney to the Tree at lv52). So, on my next party, I try to keep record on our XP/hr. With me doing fully mage vs. keeping up my duty and melee, the XP/hr has no obvious difference. In fact, we gain around 3.2 XP/hr as me being purely mage and 3.5 XP/hr as me being mage+melee.
I am not trying to say that a RDM that melee will make a party better. Considering that I chose to be a human RDM because I love the versatile of it, I simply do not like to stand back and act as a WHM+BLM with 60% of the power. I would rather act as WHM+BLM+WAR with 60% of the power. Having a SMN sub, I hardly ever run out of MP before the convert timer expire.
After all, this is a game and people suppose to have fun. Yeah, there might be a "formula" way to make things easier or make you being accepted by most people, but play the way you want to and enjoy it, as long as it doesn't hurt the others.
P.S. One thing that I realized is that once I got refresh, I hardly find it benefit from rest when I need to do my enfeebling, refresh, dispel and even sometime triple MB with my 2 BLMs accordingly (especially on crab and crawler and beetles). It is not saying that I don't have time to do it, but sitting there doing nothing to regen might be 15 mp in 10 seconds does not really benefit me mathmetically. Since at that timeframe, the mob might need to be dispel or mages might need to be refreshed. Again, no absolute right or wrong answer, but merely a personal preference.