I jsut cannot see the validity of such a suggestion, as I said it has absolutely no purpose other than to make the game harder for others.
So if all this has been said, what is left ? - to pull numbers and percentiles out of thing air and argue the workings of something that when you pull it all down to it's core, is just a method for a player who has been playing for 5 or more years to make others have less fun.
Clearly the player making the suggestion does not like to "chug their way" through quests, but there are some who do.
Now, one of those players can make a choice and play the way they want with the current system, it is not hard to say "Ok, I'm not using mana pots unless it's at least 5 minutes between", but if the system is changed then those players that may wish to chug away now cannot.
So in that respect it is nothing more than changing the way others play, and has little to no bearing on the OP or players who think that way.
If this was a primarily FPS / Deathmatch / PvP type game then sure such an argument would be valid, but it's not, it's a primarily PvE MMO game.......
I really don't see any other argument for it. There is nothing left.