2nd boss in NW you basically just have to dump all your weapons into them and hope you kill him before the 3rd wave of adds. The problem is just dealing with all the trash before the 3rd boss. It takes 8-12 minutes to clear it all and the last boss can take like 4-5 minutes on +15 on tyrannical week.
necrotic wake second boss
plaguefall first boss, last boss. positioning is important. last boss if you have delay that you dont notice, in your screen you are clear but tentacles hit you and you die instant. that sucks.
de other side last boss , dealer boss
top: butcher boss ,last boss (without lust)
are the most difficult for me.
Agree with most comments on here. A lot of players will feel like noobs once they are pushing 4+ on nm and plague for the first time after finished mythic 0. At around il 184.
My resto druid is 780 rio scored.
but i had what you said with my outlaw rogue 196 ilevel. pf +3 tyrannical
all the other guys are around 185 , they all friends.
pf first boss mm hunter had 800 dps 
while i had 2.1k dps(it is low actually i was testing my sub spec. )
anyway they did not kill little adds in time. big add cc was problem.
Probably they were cheesing on m0. means they cc big add, dont touch littles ones, only attack boss.
anyway we killed it after 3-4 wipes , second boss we wiped to explosion add, i checked mm hunter was again 800dps, i just left. would not make full run in 2hours.
I was able to do +12 Plaguefall on Tyrannical week but it was massively hard compared to all others. Our group hit a wall on +13. The last boss is absolutely insane and we had 2 dispells in the group. It is indeed overtuned.
Plaguefall is a awful. The amount of unavoidable group damage on some of those bosses is nuts. I don’t mind Necrotic Wake as much, but it’s definitely not one of my favorites either.
You don’t have to kill the Frost Mages. CC them and they will despawn without buffing the boss. Naturally you have to kill the warriors, but CC’ing the caster will prevent damage and increase uptime.