hard mode dungeons are suppose to be hard for a few reasons. most importantly is better rewards that makes it worth farming.

i farmed hard mode 6 of fire knight dungeon 23 times with super raid on and got zero mythical gear.

an important thing to point out is that hard mode dungeons should never drop rare gears. It's pointless to farm hard mode while still having higher chances of getting rare gears and the least chance of getting a Mythical which is the sole purpose of the hard mode dungeon in the first place.

just my thoughts