Do you even know what "Mid difficulty" is?
So your "mid difficulty" dungeon has to let your robe class survive while you facetank his complete attack pattern? That's a ridiculous requirement.
Low tier dungeons are up to 452 now,
after that you have 5 dungeons to run (AA, GLS, GV, AQ, DA) who are nerfed to NM standard with some HM mechanics that are not even oneshot anymore if they used to be. No attack there is gonna one shot even a robe class with +5 gear that is not one shotting a plate class either.
just a matter of learning mechanics.
Worse is, not even in +15 Kaia you can rest, even in Normal Mode.
Still, just know mechanics and you are fine.
AA - learn what to do during red magic at final boss and nothing is gonna harm you there. rest of the dungeon doesn't require reaction time at all and is visualized pretty well.
GLS - first boss is about flower colours, second is not gonna one shot you with anything besides someone caught a colour and is being targeted (easy to avoid), last boss is now even counting for you and all other attacks don't one-shot anymore or bring you in danger to die.
GV - healing mechanics are nerfed so that you don't even need one anymore, last boss is about 2 colours being changed every minute.
AQ - Recycling of bosses: version 5 and 3. If you play for that long, these shouldn't be a problem at all - again, no one shotting attacks besides first bosses colour circles
DA - You even can practice in a Solo Mode, very good implemention to avoid people having no clue about the dungeon while everyone can practice for it.
There are like 1-2 things you have to learn in these dungeons and everything else is "boss hitting the tank". If you still have problems in +15 Kaia gear you should not buy the gear in the future...