Yeah, the T8 Knights are a pain if you're not prepared for them. The Knight Castellan has an especially heavy footprint on the meta right now as it's both very killy and very hard to put down. Seems to come almost standard with the Ion Bulwark warlord trait too.
So not only do my poor Sisters need to get into range through its withering fire, then the meltaguns that hit bounce off it half the time, and half what remains gets saved. Never mind Rotate Ion Shields potentially making it even worse
Two Knights in a 1000 point game without a warning beforehand doesn't sound all that friendly TBH. Hell, I tend to remind people to bring enough anti-armour against Mechanized Sisters
At 2k points though, you should bring the tools to deal with a Knight. Someone may show up playing Imperial Knights and nothing else except maybe a small CP-generating Batallion. Vision blocking terrain is your friend.
Anyway, back to list-thinking. Can't only think of Knights, have to deal with all comers. Well, 2 lists means you may have the option of picking which you use for each game so you can specialize at least one of them, but let's think all comers for now. Chapter Approved 2018 means a large reduction in point costs, but you'll want to check if the Beta bolter rules
Actual stab at a list to be made when I'm fully awake.