I'm not saying you should play that way. Not every one has the time or the commitment to do that but it's definitely a more enjoyable way to do it.
I don't really agree, or atleast I don't think I do and I'm not willing to invest the time necessary to find out. Even a fast playthrough will need 12 hours to beat the game (according to a friend that has also played through it multiple times).
Besides, it's not like I'm not going to do what you do. I'm gonna play with a strength style, and an arcane and BT style. And given that the enemies hit harder and get more health in new playthroughs, even the fact that I'm leveled up beyond normal means won't matter eventually.
Assuming the game is still fun to play, I'll keep playing. The difference is when you want to try a new build or weapon (atleast if you were playing it for the first time like me and didn't have the 4 builds already maxed out), you're going to have to grind from the start again, while all I'll need to do is go to the menu and switch the weapon. That, imo, makes it worth it. 4 hours grinding already gave me a second Stat build. It will take more for the third. Only the fourth will really be a ridiculous time investment, but I might not bother with that. In the case of arcane, I just want to use moonlight sword. I'm. More okay with missing one weapons than all but a few.
Plus, I feel people are overselling the tedium of grinding. Sure, it's more tedious than going through the game as normal, but not much more if you already played through the game multiple times before, and the combat still being fun as it is means it doesn't get as old as, say, pokemon grinding.
Edit: oh, that's another thing. What about upgrading weapons? That's another think I have a fast trip to doing if I grind vs starting a new game.