Okay, so I think I'm at end game, anyway level 42 or something and the story is finished basically i'm running around doing random missions and tarot trying to get my 'gear score' up to 1400 to do the highest quests.

I will start with a couple of questions:
what else is there to do to keep progressing?
if difficulty is not impacting drops or making any decent adjustment to fate gain, what is the reason for upping the difficulty?

Now, on my journey I have encountered some really irritating balance issues with the grinding gear process, I am not sure about anyone elses experience, but I get maybe 1 relic every 20 hours outside of tarot missions buffed with Extreme Fortune, and even then it requires a lot of fate and a specific type of map, ideally i'm doing assassination on the small swamp map with the secret area. Ideally I could just play random and do my thing, but doing assassination beats being stuck in a 3 game loop of doing nurgle warp gates (yes that happened) and losing 300 of my precious fate & 3 charges of Extreme fortune for nothing at all. Now I am almost out of fate and back to the grind where I don't get any drops at all, woe is me.

• The cost of fate: Earning fate to do tarot quests outside of rewards is insane, in theory at an average of 8 per quest that is 12 quests or about for a single tarot mission. 10-13:1, i'd say the the fate cost of tarot needs a massive reduction 3:1 or 5:1 would be much more appropriate. Especially considering how some tarot maps spawn zero bosses and no chance of item drops.
• Map balance is terrible: All quests are not created equal, this means  that if you get a nurgle warp gate quest as you tarot mission, you are pretty much screwed for items, unless you get on of those lucky elites that has mirror image. Whereas if you do assassination quests (which you can chose, and you get 3 Ubers (e.g. tanks) to kill and a secret room, you're away laughing.
• Relic drops are too infrequent: I get no relics at all unless I am running a Tarot mission with extreme fortune, irregardless of whether I crank the difficulty up into the red or play in the green, irrespective of gear score, actually I got plenty of Relics early game but now that i'm playing 1400+ I get none.
• Tarot Missions  Random?: I think the tarot missions are supposed to be random, but if you do several in a row, it continues to spawn the same mission, I was doing the armor one and so the mission is listed as chaos demons or other and no mission type specified, I get 3 x Warp missions in a row, and due to the lack of ballance between the missions in terms of item drops, this was insanely frustrating.
• Crafting is OP: Only through going online I found that crafting could improve relics greatly, and it is insane, I went from 900 - 1250 in the space of 10 minutes, yet that did not impact my game at all, i still get the same (lack of) drops as before and everything is basically the same. IMO you go too far too fast. The mechanic is also quite broken, as a high level two handed weapon provides the best upgrade far and away over anything else, I have two level 40 weapons, the 2 handed sword is instantly 25% improvement to max whereas the same level 1 handed sword is providing a 4-8% improvement, seems broken to me.
  
  Really end of the day where I am with the end game is bored, I can't really play to get new relics because the fate grind is too massive, and the idea of getting one of the 'bad maps' is too large. Relic drops are too infrequent doing regular quests, and there doesn't really seem to be anything else to tide me over.