Since we have crafting in the game at this point, it makes sense that trinkets and rune arms SHOULD be items that can be randomly generated in the loot tables. I am not suggesting they be overpowered, but at the same time, trinkets have been in the game since launch, and other than "named items" which can not even be used in the crafting system, there has never been any mention of trinkets that are just randomly generated loot the way you see with other items. Rune arms are a new concept, but so were outfits for Monks. You have the named items which are more powerful than the vast majority of randomly generated items, and that makes them desired, without them being exclusive "named" loot.
DDO has come a long way since the initial launch, but loot is still an area that could use some attention, and I am NOT talking about the high end stuff just to make already powerful characters even more powerful.