As example:
You meet the Boss in first Room, small tiny Robot with just a charge "punch" -> R1 (Room 1)
Simple mechanic and you can experiment different strategies with many possibilities in which jobs you take.
After beating it, he runs back to the next room.
Your Progress is save once beaten you can always start from there but you must not (farming gear for friends)
Charge is a "onehit death" to the first player in line (you can sacrifice yourself to protect someone if needed)
No weekly lockouts or any other of that crap!
You can break and rest until your static meets again, maybe on the next day to follow the robot into room 2 -> R2
The Robot now changed, added Wings and can fly (you will see when fighting him).
Lets say the wings giving him a divebomb like mechanic in ADD to the already known charge punch.
For now (he just uses 2 mechanics) you can let him do it randomly.
The new thing is one player gets a marker and then you see the animation about the boss flying (you cant attack him).
The marked player must MOVE to prevent damage and you may can add AoE range, so the marked player have to split from the others.
I am not a friend of onehit death mechanics, but to make it simple for explaining just lets say every mechanic is a onehit thing.
After beating, its same as before, he could escape to the next room...
Same with loot as before its free for the players to choose how fast they farm!
Server first groups will go in every day while others may just go in once a week, let them they dont destroy anything!
Allow freely helping others (carrying or such) but dont allow content selling (carrying for real money or gil) - partyfinder as example, then they cant trade
Now in Room 3 he will get again something new, lets say a Plasma Gun (shared damage) -> R3
The key is to NOT change the previously learned mechanics or you throw away every progress made so far!
If you dont see the little trick i made: Wings (= spread) but Plasma Gun (=gather)
The Charge Punsh is meant to kill one (you have to revive) later one i thought to add some Buffs where you can pick it up and get invulnerability for a short time to take the punch.
The idea behind is, if you have about 5+ or even 10+ mechanics maybe some simultaneously, you may add some "helpers"
However that all depends in which direction you gonna design the fight.
This is just an example and was made to show a common learning curve. While server first groups are bored with R1 to R5, they gonna like R6 to R10...
The Key is that if there are 3 mechanics you must only learn one new, in add the more you move up in Rooms the easier you can handle Room 1 mechanics because you have it in the other rooms too...
While the brain focus to learn the new mechanic it can rely on the already learned mechanic counters and in result its less frustration and stress because you "know what to do"
If you cheese Room 1 with 8 Healers, who cares? You cant do it forever in the following rooms ... if players like to cheese, let them!
Why not, Room 1 with a lot reviving... well, that's why I mentioned to add later some buffs because you can not keep that up for all rooms...
It was a very very simple example and needs a lot balancing too, but it shows pretty good the difference to what we have in FFXIV and why there is so much frustration!
SE keeps some mechanics "same" spread over more bosses but the problem is there is way too much "new" stuff.
You can not expect from a player who plays 1h a day to learn a dungeon with 5 bossmonsters within a month.
Yoshi-P himself said: Watching a video is one thing, but succeed the same way as seen in the video is way harder!
Just for the sceptic: I said its just a simple small EXAMPLE - imagine 100 rooms where the Robot adds and loses Robot parts (he is not always using the 100 mechanics) and then imagine YOU can influence what the Robot does depending which Room you go "next" (example: if you can choose between 3 doors, please NO RNG)