This fight over who's better or more needed in a group is pointless to me sometimes. Fact is, every PuG only ever wants ranged classes in this game sadly, because SE thought it would be a good idea to build most of the endgame content to be alot harsher on melee. I've lost count at the amount of times I got turned down with the message
"No melee". or Just looking on PF and seeing only ranged DPS positions and if you try to make your own group, guess what? no one joins
The only way we get a group is either by forcing our way in through duty finder (guarda, titan ext etc) or being in a FreeCompany.
When it comes to PuGing Coil however, DRG is always goona be chosen over Monk, because there is always going to be a bard in the group and someone needs to press the LB button

People tend to prefer Disembowel over Mantra which DRG can also get btw.