[Gorothir]

My experience is that they obviously update the database from time to time, but never completely, so many items remain unavailable.

I can not deduce how they do it, it seems that they copy some items from the "real" game database that contains all items available inside the game to the data.lotro.com-API-database or something like this.
Or perhaps when they design new items for the game (e. g. that level 76-85 stuff recently) the save-process tries to insert into both databases but fails on the data.lotro.com-API-database for some reason.

Finally I can say that there are many items missing in (nearly) every level-range, it seems that the covering of lower-level-items is greater than higher-level-items (66 and above), but this may be just an impression of myself.

It also seems that my.lotro.com now uses another method to load the images. I tried with my main-char, a captain who has an "Intricately Wrought Riddermark Standard of Hope", the corresponding image (but without information) is now displayed in my.lotro.com.
If I access that over the data.lotro.com-API, I just get the name of the item in the character-query, if I try to load the item over the id with an item-query to get the image and additional information, I still get "Unable to retrieve item data" from the data.lotro.com-server.