I have been playing this game on and off since a realm reborn and have been enjoy this MMO more than any other to date.
Playing Dawntrails Trials and Arcadion bosses have been fun so far, and I will continue playing Arcadion every week.
But my biggest complaint though has to be a few of the dungeon bosses.

I believe it's easier to do dungeons with other people compared to trusts.
With people they are able to rez you if you die or let them carry you like most people, but in trusts if you get hit once you die and have to restart the boss from scratch.
As I was playing Viper through the MSQ there were 3 bosses in particular which were a real pain in the ass in which one of them took me an hour to kill. Not because of difficulty but because as you follow the trust team members the boss mechanic always manages to deal damage to you and that damage always 1 shots you.

The bosses are:
MaulSkull from Skydeep Cenote
Antivirus from Alexandria
And the champion that took me an hour to defeat The Herpe master, "Herpekaris" from Origenics. This boss almost made me quit the game.

I was having a miserable time playing these dungeons that I don't understand why they don't just put dungeons as end game content instead of it being attached to MSQ's.
Trials I don't mind because I enjoy doing those with the MSQ.
As for all the other dungeon bosses they were fine especially my favorite boss fight in the game, "The Eliminator" in Alexandria. This boss fight was fun as hell.

So, after I reached 100 with Viper and finished the first week of Arcadion I decided to level up my Tank through dungeons doing trusts. Guess what happened?
I was having fun. This is when I knew there was something wrong. I was purposely getting hit with the attacks that 1 shotted me with my viper and it took a fraction of my health away. This is why people who play tanks are not complaining because it's not difficult for them because they can't die. Unless they fall off the edge or through a hole. The game shouldn't be designed this way.

Without spoiling the game, the last trial boss killed everyone except the 2 tanks and those 2 tanks were able to kill this boss while it still had 1/4 of its health left while we were waiting for about 5 minutes for them to kill the boss. This shouldn't happen. Tanks should be able to die just like everyone else.

So yeah, I don't think difficulty is the problem, it's the damage these mechanics deal. Especially since most of the fight you are dodging mechanics instead of fighting the boss. You will see casters casting spells halfway and they have to stop to avoid a mechanic. Summoners die and they have to recast their carbuncle which I believe should be an instant cast.
So yeah, my advice to those who are unsure what to play in this game. Play a Tank it's the most fun you will have.