Obtain your heirloom rings. Ghost Pirate Rings can be obtained via Shipyard missions. You can equip one ring from this category. A Dread Pirate Ring can be obtained via placing at least second in the weekly Stranglethorn Fishing Extravaganza, which on many realms is a very competitive event. Note that to obtain the Ghost Pirate Rings, you will need a max level character with a garrison of at least level 3. You you will also have to develop your Shipyard to the appropriate level to receive the mission. Your other heirloom gear will still give you a big boost if you choose not to go for these.
I think this may have been a case of that specific sword simply having wildly inflated secondaries. If I recall correctly, when I played during Wrath, +STR and +Hit were the stat kings for plate DPS classes (I remember all the guides recommending +STR gems in every slot and +STR enchants on everything) and secondary stats were, well, secondary, and inflated secondaries on a weapon weren't that big a deal. But now that secondary stats have so much more importance, I suspect that an "outlier" weapon like that just wreaks havoc with modern calculations, so that all the addon sees is that this particular sword offers +15 more Haste and Crit than everything else that drops.
I've used WoW-Pro for years and in WoD, Legion and now BfA it's been awesome for just going on auto-pilot and working your way through a zone. It has 3 levels of depth you can set, so you can set it to just do 1) the main story, main points of interest and rare mobs and treasure that aren't far off the beaten path; 2) every quest with a more thorough dive into the side stuff; 3) absolutely everything.