I come with presuposition that I:

1) know the areas typically used for ranking;
2) know the often-travelled areas;
3) script my area-explore routines the first time I learn it, so when I do it with a next character I just go "exploreHTOS" and run about it in a few seconds; doesn't work with many areas with agro mobs, but most of the time it's fine;

What I say is that for me (and I consider myself not being unique) edge incentive beats other incentives for exploring new areas. So if you remove obs/exp, I most likely will stop exploring (not that anyone cares, of course, but e.g. those awesome two hours I've spent in Kobold Warrens would certainly be missing).

P.S. I didn't encounter a single nightgaunt in 10 months I've been playing.

P.P.S. Thanks to Umiron for Kobold Warrens hint, that one led to an exciting experience.