That was exactly why i made this post, as you said some of them are just ugly, i myself tend to stick to just the Ironworks Magitek Degen because most of the other RDM arms look like they were just copy and pasted with new colors or names.
But over all to date the fact that the off hand slot is not being used makes it a pointless thing. If they are not gonna change this for RDMs and a few other classes they should make PLD arms like RDM arms and remove that slot all together.