It's a bit of a dead-end of a discussion honestly. We're basically all arguing to have a game tuned towards our personal gameplay preferences, so it's not even a debate, it's a collection of extremely biased opinions.
My usual playstyle is as follows:
First playthrough on Normal or Hard, so I can figure out the systems in a relaxed way and enjoy a bit of storyfagottry. I also absolutely refuse to read or use any outside resources, build and itemization advice, walkthroughs, let's play, whatever. I play it oldschool like it's 1985, no internet unless I'm really totally stuck.
If I like the game enough I do another playthrough, but this time on max difficulty, everything min-maxed to the bone and use every resource available to pimp up the party and make it steamroll the content in most efficient way possible. In PoE this also means using custom companions.
So for my playstyle unlocking companion customization only on subsequent playthroughs is a nice compromise, but for somebody else it might just not work.