To be more specific, the raid acquired items? Group boots don't show that modifier, unless I'm missing it.
No, you are not missing anything but I did. Forgot group gear did not have that. I have the T5 versions and noted that the T6 version/final evolved ones do not have back stab/other melee modifiers.
The mods are inconsequential, this has been brought up numerous times over the duration of the TBL expansion and numerous times has it been acknowledged by Ngreth and labeled not a bug. You can probably find info on this via the search function on these forums.
So rogues that choose to use this gear (which is better than any other gear currently in game in regards to stats) can't reach our full potential in backstab modifier? It isn't a bug, it is an oversight.
You wanting it doesn't mean it missing is an oversight. Ngreth specifically said he didn't care about it and he wasn't adding it to it. Its immaterial dps. Tanks looks +bash too.