I'd rather someone brought Battlemaster than lvl49s. In many cases, a Battlemaster piece is significantly better than the equivalent Columni. I've often hit 50 with 3.5k ranked WZ comms, and 2k normal comms, and moved into nearly full Battlemaster. Storymode operations are definitely do-able in that condition.
Also, many, many theorycrafters argue that BIS relic for almost every class is the Warhero Relic of Boundless Ages (situationally slightly less attractive than matrix cube). As far as I know, there is nothing better.
The reason PvE gear is such a huge disadvantage in PvP is expertise: there's no equivalent for PvE. Yes, your stats are slightly lower than equivalent tier PvE equipment (often most pronounced in terms of HP), but you're not doing a solid 30% less damage or taking a solid 30% more damage.
In my experience, severely undergeared players who know what they're doing can perform very well in PvE content. Even a very good PvPer with zero expertise is going to have an extremely hard time in Wzs.
The majority of your statements fit into the category where PvP gear > under geared players. But that right there is already a problem since the player you are comparing to is under geared for the content. It's the worst player to compare to. It's like comparing a full rakata set to recruit gear, you just don't do it.
My point is that the bonus (or lack there of) of using the wrong gear is pretty equivalent. You can use high end PvP gear to clear basic PvE content just as you can compete in normal PvP matches with high end PvE gear (You only get destroyed by people in full BM/WR gear as expected). Both sets would fail miserably once taken to the higher end levels (Ranked matches/ EC).
Also, the relics are the exclusion since the abilities don't involve expertise. (If you could use the PvE relics in PvP, wouldn't you?)