Actually to be honest, I’m constantly switching the 3xDefender and 3xSwords. On several test matches, I found that a 2nd wished Sword can still be destroyed pretty fast by minions but Defenders stick a little more because the opponent need an added ping or one more minion. My mind is not set on that, and I’m still hesistating …
Also : Defenders draw a lot more attention for removal, that’s less for the next bigger threats … and they don’t die on a simple Plasma Storm/Frostburn, I prefer to play a Defender agressively where I used to play a Sword more defensive, on the back, hoping to get a buff before it’s killed.
And finally, as pointed before, the 9x mechs are enough to get a Mechaz0r out. When it comes to the late game, I prefer to draw a Defender than a Sword 
I added more for consistency, because I want less cards types and more cards “outs” (poker style). With 3xAstral Phasing, I also allow myself to make a Defender or Aymara fly when it’s needed 
Maybe this last update is less effective than the previous one, it’s constantly evolving with the meta, sometime better, sometime worse, I’m far from being a deckbuilding wizard 
Edit : one minion that is “just ok” but I’m struggling to replace on this version is the Wind Shrike, still searching for something with more value that fits this deck at 5 mana.