I've got this same dang faucet, and it is leaky. There are some answers in the linked page, but there are some contradictory posts, so I thought I'd re-pose this query.
There is nothing to unscrew or put a hex wrench into up top.
Is the answer: pry with a screwdriver until handles are off? They're on there pretty good. Also, I'm not even sure what brand this guy is, so I'm fuzzy on exactly what cartridge to purchase to fix it.