I dont believe mercenaries are suppose to add to origin characters ... they are suppose to replace them.
Party of 6 could be usefull in many ways ...
But mercenaries are not good argument for it, as far as i know, if you would have party of 6 ... there is litteraly nothing forbiding you to make 6 custom characters, instead of 4 ... And (speaking about single player, obviously) you are just where you are now. :-/
In the end there is nothing disrespectful, or insulting about mentioning that some thing is obvious ... if you find such statement as personal attack, i believe you have problem. :-/
If my comments bother you, there is nothing easier than telling me to stop. I mean ... I won't ... but it's easy to say.