Unless Amazon makes the flagged bonus for level 60s equivalent to a max luck set, which I strongly doubt they will do.
PvPers can’t viably wear luck gear. You can equip it obviously, but perks are the differentiating factor of gear in PvP (GS is scaled). Wasting them on things that don’t help you fight is terrible and will simply lead you to dying more.
Some players are concerned about flagging feeling obligatory. Right now, we are in a situation where flagging (once you max level) is clearly a detriment. The proposed changes brings it closer to neutral by addressing the fact PvPers can’t stack luck (without giving themselves a separate severe disadvantage).
The ideal game state is that both playing flagged and unflagged are equally viable, with their own costs and benefits. Then players can do what they enjoy most. The changes help push us closer to that. Nothing in game or proposed is close to making flagging more efficient or beneficial for a player.