Scrapper question

Yes, but due to Diminishing Returns it takes around 105% Def in PvE to equal 45% in PvP.

Actually, I haven't tested that in ages, as I was one of the casual PvPers put off by the I13 changes and I haven't PvPed except for Shivan skirmishes since I13 beta. I'll run my Stalker into RV in a sec and verify the A and B factors for DR on Defense.

Minute nit pick - the soft cap is 45%, the hard cap is much higher. It's called the soft cap because it is the point where extra defense stops helping you against normal mobs. If you face enemies with either tohit buffs or significant defense debuffs, then any defense over 45% will still help you.

Sorry for the recap if you already knew that, but it leads into the next bit...

This isn't the case (it never was, even before I13) since players are far more likely to have tohit buffs than mobs. Build Up, Aim, Focused Accuracy, Rage, a Kismet, yellow inspirations; all these things would break the 45% soft cap. When fighting players, I'd consider more defense to always be better.

As Kosmos points out, however, there is very harsh diminishing returns in PvP now, so after a certain point getting a meaningful amount more defense is extremely hard to do.