And it takes almost no effort to overgear any 4 man content barring HM LI, and little enough effort to overgear HM LI.
One can be wearing full Columi (or better) gear in less than a week of hitting 50 without legacy transferring anything simply by doing at least 1 GF run a day, and that already puts you into "overgeared" status for all world Heroic 4s and all T1 HM FPs.
I would think trying to 3DPS something like HM LI with wacky specs like DPS Ops/Smuggs, 3x DPS Sorc/Sage, etc. would make it miserable, but anything easier is basically a non-issue.
The issue isn't how easy it is to overgear content. The point is that the need for a tank is reduced (or eliminated) when you over gear it. Hell the need for DPS is negated if you sufficiently overgear it. A lot of content in this game can be soloed or 2 manned, so there isn't much point looking at those instances. Consider group make up when it is important: at an appropriate gear level.