take this with a cup of salt not just a grain. but a couple idea's.
1. you have the shield and helm that you'd certainly wanna replace the set with. those alone are definitely a good reason to swap.
2. an eth warp blade shark runeword would be one of the best weapon options if not the best.
3. armor, rebel rw is probably one of your better options damage output wise. a curanderra with max res jewels for very specific boss fights or purify bosses but idk.
4. windrunner boots look pretty solid too. maybe epicenter which like curanderra would be specific to some purify bosses where your own damage is limited. and you wanna invest more into those. curanderra + epicenter w/ cold/fire just sounds really potent on purify fights as you don't care much about your damage at that point. and the chest frees you up for needing certain jewelry to meet the 50% dr. and a very high hp pool.
5. dex is important up to max block. past that it's more damage but not much else. so it would depend what your doing and trading it for. if it's a 5% dex amythest or something you can replace it with a 2% dex + ll/LoeK/LoA + fhr/fbr/ias (till breakpoints). after that maybe look into some of the unique jewels. It's pretty cost benefit at that point though. what are you losing, do you maintain max block/breakpoints, what are you gaining, and do you need it for what your trying to do.
6. idk the best time to switch honestly. if you think content is relatively easy that you plan to farm then why not. with the circlet you have and a shark rw weapon you need nearly no other damage source to obliterate duncraig in a very short time. idk so much about fautz, but a rebel RW in addition feels like it would do the trick. IDK about teganze, once i get to test it i'm going to see how a samael sword harbinger melee sorc does in there. seems like it could work with how much +physical damage we have, and sammael sword damage scaling on str & dex.
note: doesn't phys res cap at 50%. your hp seems a little low at 8k. assuming no fire or cold specced in.