Not to mention many bosses it would be counter productive to bring a melee DPS as apposed to a ranged DPS as they would not really be able to do things without dying or loosing a lot of dps such as Sewer Slime, Mutated Rat, Airship Boss 1, Minotaur, Gorgon , Abandoned Mines Boss 2 , Mist Keeper Raid boss 1, Raid boss 2 , Raid boss 5.
The reasons why are as follows:
Spoilers
1. Sewer Slime
Self explanatory, the boss is kited for the entire fight and melee dps will die if boss swaps agro to them.
2. Mutated rat
Boss is tanked in the poison, Melee dps would die really quickly or need to hop out before death loosing a lot of dps.
3. Airship Boss 1
Boss has to be re positioned occasionally due to poison pools loosing dps and causing potential death for melee DPS.
4. Minotaur
Orbs exploding on the tank would hit a melee dps wherever the stand killing them, they would have to move away from the boss loosing dps.
5. Gorgon
Melee dps cannot get the add without potentially causing a party wipe. This is the one in this list where it would be acceptable to bring a melee dps but it still has flaws with the play style.
6. Abandoned Mines Boss 2
Melee dps has little time to dodge magic missile, pools can cause melee DPS to stop attacking due to properer placement. This is the other one where it would be acceptable to bring a melee dps but still has flaws with the mechanics of the boss.
7. Mist Keeper
Melee dps could cause damage to the tank during yellow mist, during green mist the melee dps cannot attack at all, slams would be hard to get out of, if the class does not have a movement ability then it would be impossible to get out of the slam once you see it start to be cast, the only other option is to jump out earlier loosing even more dps.
8. Raid Boss 1
Add has a poison pool which could kill melee dps. Boss is usually kited on hard mode.
9. Raid Boss 2
Similar reasons as to why shamans are not good on the fight. It takes a long time to switch to the adds when boss starts to glow and vice versa, the melee dps can cause shockwaves really close to the tank which can be hard to avoid to near impossible if not called out.
10. Raid Boss 5
Melee dps cannot hit the add well as it constantly moves. Melee dps have to travel a longer distance to the circles which could cause party wipe. This boss is also sometimes kited on hard mode.