To make a game like POE 1 and 2 really work they need change things lot.
Having it made so a person can do a single player character run through bad idea as either becomes impossible to do single player run or it just not challenging enough for group.
Just choose or if got have both have check box for person doing single player character run, that tweaks difficulty for said run.
Empower just crazy way it is, as just can rest any time without any issues. Empower scales 10x up what ever used and can be used every fight. Resting also increases states from food to and food not challenge get. There not real financial challenge so you can afford every bit equipment.
Level progression should be gradual curve and enemies should scale to that curve. Boss fights dragons etc should be few levels higher then rest. You should always feel challenged but not frustrated. Need keep some attrition like per rest from POE 1 so person can scale difficult for themselves to point. POE 2 has not real attrition system player can use to scale difficulty as per encounter system doesn't play well for it. Can't try lowering little of this make that higher while the progression curve is off, as you need sort that curve out first. playing with this and that will make start game more frustrating while not fixing the cake walk that happens after leaving city in POE 2.
Fights in area really need good planning and placement stop having trash fights. Example if we build pirate stronghold then first think what sort bad guys can we use what fits said theme firstly pirates what else undead pirates etc. Then need define where put fights and each choice need think why here, what advantage would they have been this placement? What difficulty are we catering for how do we want difficult scale as player run through dungeon.
AI needs serious help as it trips over itself, always goes for easy target and can easily be pulled through chock point. Teach AI gang up fast attack on one of a party doesn't need be weakest. Teach it not be stupid chase through choke point.
Magic has to be scaled, yes nice have powerful spells but they should be very special not useable every fight. Per encounter and open world just way to many variables to make every fight really fit right level. Open world never know when person going go a to b or from a to z.
Equipment yes we love finding new equipment but legendary equipment should be very limited.
People always want everything but ask really rich person done everything gets bit boring cause there nothing special left for them as got everything. So in games people want lots but don't give all easy or let them use special things all the time as stop things been special, make people work hard get special things or be able use special things.
If want build game that's per encounter and open world say it from first game and stick to it, don't change it so much system becomes something totally new. Can't please everyone design it for one set of people and stick to that. Changing systems pushing people out pull in few new, few new might not touch it based on some scared start franchise mid way through.
If your going do attrition system then needs to make people pay price for using example per rest needs have chance of been attacked when rest out in wilds. Per rest needs make people pay price for going back to town half way through dungeon each hour away from dungeon it refills said dungeon with bad guys, therefore after number hours said dungeons back to fall up.
Honestly what ever system you have try have things that can be turned on to make it more difficult. I played tyranny and POE 1 so many times would be nice I can turn things up make it more challenge at times. It's really nice be able tweak game to fit your personal level at various times.
Personally if I was obsidian I make POE 3 and use POE 3 set how you really want build it per encounter or per rest. Used it to really find way balance scaling and gradual curve of levelling up. I would make POE 3 end watcher story. From that I start again with new story and character set in past or in future and build that franchise using what you learned from this set stories.
I very want see how story gets completed. I be here for POE 3. I also want meet kyros in tyranny see how that works out for my fatebinder. I like see you build new story and for you really make it truly legendary set games that really push story companions and exploration.
Honestly want an open world game need do away with levels as we know it and have one fixed level define whole your character at start game, but if do that need reward player in different way and you need make sure story lines and companions are great and amazing.
Have semi open world where to progress from an area need to complete set objective to progress, that way easier manage level progression and level scaling.
I don't dislike POE 1 or 2 or tyranny and not complaining as want you follow my way or nothing. I write in forum because want you build best games possible and I want play them in 20 years time want still remember them because they where special.