I believe that list is accurate.
Spam a mix so you can upgrade t2 shields to t3 to instantly turn the shield back on. Also the mix can help to create shield overlaps on the structure(s) you’re defending.
You didn’t ask this but the way you defend against a Mavor is by assisting a single t3 Sera or Aeon shield with a ton of build power. Like ~40 t3 engineers or fully upgraded hives. This will never drop vs a Mavor that’s ringed with t3 pgens as long as you don’t stall either mass or energy. This does play into how you defend against t3 arty and Novax as well, shield assisting is a very strong mechanic.
If you micro the snipers they’re very good if you’ve got room to kite back. If you don’t have room to kite then they’re bad unless you made what is probably far too many of them.
No clue on the last one. I think I remember t3 arties being changed to be more similar between factions so there might not be a huge difference there anymore. Not positive though, it’s extremely rare I make t3 arty.