To me, sometimes we can do all bosses and sometimes we’re just going to kill the main boss, and other times we just suck at things.
So how hard is it for you guys? It feels like the game designers didn’t really care about what’s going to happen in a dungeon … Let alone all other games out there allows you to have a healer, but this - nope. Figure it out, yeah? 
Each class should have their own tiny heals that can do at least 25% heals or something.
Without tank and cleric is hard, only tank is ok.
lmao
If it’s too difficult to buy potions, then I suggest to create parties manually, so you can be sure there will be a cleric.
I have only played up to the LV 115 dg and it was ok. At least until now I prefer to have classes with good AoE and mobing over healers or tanks just for the sake of speed.
reach 130 and mobs will eat you like everyday breakfast without healern
It’s hard as a tank if the mobs are way higher than you. I still remembered when I first entered 190 dungeon more than 1 week ago and I didn’t realize that mobs there are at least lvl 200 lol. Lvl penalty is ruthless.
How hard a dungeon would be is clearly dependent on player’s skills and mechanics. You can have the perfect class combos and still lose if the players lack the abilities.