Set dungeons mastered 12/28: rathma, trag’Oul, inarius, pestillence, tal rasha vyr, arachyr, maraudeur, akkan, invoker, seeker of the light and imortal king.
Set dungeon with only primary objective(6/28) : Firebird, Inna, Shadow, UE, Natalya, Roland.
Set dungeon without objectives (10/28): Delsere, Helltooth, Jade, Zunimassa, Monkey Kings, Raiement, Uliana, Raekor, Might of the Earth, Wrath of wastes.
In the last group which are the easiest ?
All set dungeons are easy to complete. They all have at least one primary objective that is easy to do.
Mastering, I would say Zuni, Raiment, Jade are easy with the right gear.
I passed all for the wings and Necromancer are not needed for that. (Will pass necro dungeons in the new season 20 because i have zero space in stash for necromancer items ahahah).
Don’t remember all but there are some i do remember clearly cause they gave me hard time or annoying time hahahah.
- Monkey Kings - very annoying dungeon and it took me maybe 50+ tries to get it in season 19. The whole problem is that to master it you need bots to be kinda together into groups. And sometimes there is not just enough group packs. You basically don’t have much time to get back once you reach the end.
I had 1 bot hidding in the corner of one 99% explored map. So be sure to check every corner before moving forward. Managed to finish it with 1 second to spare ahhaha.
- Raiement - was hard for me before but it was easy for me in season 19. The whole point is to kill some bots at start then rush to the end and after that start to going back to the start to kill the rest of the bots. Get familiar with the map so you don’t waste time. They increased the time limit so that is why it was easier to get.
- Uliana or Inna(don’t remember) - This is kind a easy. The point is to gather 10 bots around you and activate the skill Mistic Ally. So you must rush in front of your mistic allies so they don’t kill those bots because you need them in group.
- Wrath of wastes - The whole problem comes that you must NOT take damage. And in the same time get some groups of enemies several times. There are some blades that you must be VERY VERY careful not to hit you.
- Raekor, Might of the Earth - I think it was Might of the Earth. Not sure which one was but one of them you had to kill all the bosses(5 i think) with 3 skills active. It was little annoying because sometimes they die fast or move and the first skill you activate at them doesn’t hit them. My advice - either jump to them and activate all skills fast, or wait for them to stop moving and then activate the skills. I think it was Might of the Earth.
- Natalya - I think that one was little annoying cause you must keep rain of vengence for 90 seconds but first time i passed it it took me 60 seconds hahahaha. So kinda you must go slower hahaha. Hitting bots will bring down the cooldown of rain of vengence but you must not hurry to activate it. You must be aware how much time left so you activate before the previous rain ends. Then go kill bots and remove cooldown again and like that. Not very hard at all.
Don’t remember much the witch doctor dungeons. I played them last but I guess they didn’t give me hard time.
Natalya
Use a weak set (but not too weak).
Bring a friend to help cleanup after you hit your goal.
I find Strafe helps with uptime
Raiment can be absolutely cheesed with a friend. You can just rush to the end and hit the golden chest while one or more friends go on killing everything for you without having to worry about getting hit by succubi.
Then you are no master if you can’t do it solo. 
but good point about doing set dungeons with friends.
Basically your friends just kills the bots while you do the specific tasks. If your friend do your task like reach the chest at end, then it will not count for your completion.
Never tried co-op and don’t plan to try it ever. 
Gratz! Keep it going!
Just a reminder to not be afraid to look up builds and strategies, some set dungeons require different skills/gear and have a different strategy of game play than the normal GR version of the set.