How about instead of making the grind easier in pvp but rather re structure the way you earn xp in pvp based on the actions of the battle eg boarding gives you x amount of xp and gold,
and sinking a ship give x amount, damage to sails, crew kills, hull damage, even maybe xp on how long the battle last's it doesn't have to be huge amount but all the factors of the battle could be pooled into xp earned and gold, also give the loser some thing so it doesn't demoralise people form doing pvp (merely just a bunch of suggestion's), doing these things could encourage more OW sailing and pvp. I personally don't think there is a grind at the end of the day you make your own fun in the game, if you choose to pve don't complain about it you chose to do it. Maybe the amount of xp to unlock knowledge are maybe a little high but honestly i still don't mind pushing myself to unlock them.