Your previous shoulders had 6-8% armor bonus on them which applied to all pieces of your gear, so it averaged like that.
I’d say try using two Sanctified Bones. 16% bonus damage to undead and chthonics is going to be better than slightly more OA I think. Only problem is you’d have to find elemental resistance, but I take it you’ve already found it on Coven Combatant Spaulders.
Overall components is something that is more or less similar from build to build because people had long figured the optimal ways. Builds with Soldier tend to differ a bit because they have Armor Absorption on Scars of Battle (which is an amazing passive I recommend to have at 8/8).
Here’s a blademaster component setup that looks good to me:
https://www.grimtools.com/calc/b28B3YqZ
Don’t mind the affixes, it’s obviously stashed.
Didn’t test it myself but there’s this cheat sheet:
Baffling. That relic was always considered a meme afaik.
Also, I just opened your devotions and it seems like your build has no flat RR. That’s a typical setup for a high end blademaster, but it only makes sense with Mythical Grasp of Unchained Might because it gives flat RR to ring of steel. For that reason my budget blademaster setup looks like that: