To be honest, I kinda like it. Though I do wish it wasn't quite so "in your face".
There was nothing worse in FFXI than running through an area, almost getting to the zoneline that is your goal, then getting aggro'd because you couldn't see something before it was too late. Chigoes come to mind.
I'm an explorer, so I definitely understand the reasoning behind wanting to discover for yourself. And the first time I enter a new area, I would want to do just that. But after that, it's just a pain to remember what aggro'd if you haven't been there in awhile.
In other words, I would agree with a toggle option, but not getting rid of it altogether (but I would agree with making the red icon less of an eyesore).