I have been delighted by the responses so far and they have given me far more to think about than I can fully tackle right now - and I want to look a few things out in HoME.
However, while it has taken me probably more years than Lush has been alive (Grade 8 is about 12 isn't it?)
to realise that there are a lrge number of this instances (and I never claimed my list was exhaustive) -I do remember thinking when I finished the book that it was lucky that only Boromir had died (and stayed dead!) -since I was only twelve and also quite devastated by Halbarad dying (that guy makes quite an impact in about sentences), I didn't regard it as a problem. Frodo's seeming death had been a factor in my giving up on my first attempt to read the book so I think the death say of Legolas would have been just too traumatic - even though he and Gimli are not essential to the plot in ROTK, they are little more than representatives (I like both characters don't get me wrong).
As I grew older, and studied Literature eventually for my degree, I got the feeling that in "serious" literature people die and there are no happy endings. So the relatively few deaths among the main characters may be and overhang from LOTR's origins as a Children's book. Nevertheless I feel that one of the books great strengths is that few characters really getan absolutely happy ending - most have a bittersweet note. Even in the Hobbit which is so very much a children's book, the death of Thorin is extremely powerful and lingers in the memory (first time a book had made me cry since the death of Ginger in "Black Beauty" ).
I do like this idea of Tolkien telling the individual's story and it is one I will return to shortly.