It's ok to do some accessories since honestly they don't matter too much to begin with and if your rocking 90 stuff in your weapon and armor slots your still light years beyond the instance.

But if your going to do it with armor and weapons at least have enough respect for other people in general to use the 55 militia/operative gears and 55 weapons
Don't know why people are so incredibly selfish to do that to groups that may have waited an hour or more, i see people entering duty finder in full crafting gear all the time so have to carry people through that are basically naked except a weapon... fun...

seriously though people doing that in instances are probably not very smart to begin with, you can spiritbond much more efficiently just grinding world mobs and can level your chocobo and group up with other spiritbonders to make it even faster.