I run around with 15-20 insight anyway, I just like to have a backup in case I lose it.
Also, I don't like magic much. Its all about doing as much physical/fire damage as you can in as short of a time as you can. I swapped the tophat for the plague mask anyway. Also, that chick sounded like 80, so...... Oh, and little tip for the witch of hemwick lane. Just kill her, ignore the minions. They are easy to dodge and the fight goes quicker that way.
Mid to late 30s bro, she doesn't sound like the woman from the chapel.
I have 40 Insight and dropped it recently to buy fire paper (and to make a boss easier... it didn't make it easier)
SPOILERS FOR SOME END GAME STUFF IN HERE