Our deck has a couple of places where water pools in heavy or constant rain; the photo below shows the worst of these. It's always done this - I imagine the builder didn't get the slope correct. (I also think he should have thought about laying the timber 90 degrees to this; the deck runs between the main house and a sleepout, so it would have made sense to have it so water could run off the ends where the deck doesn't sit against a dwelling!)

Whatever the cause, I'm looking for advice on a relatively straight-forward solution that doesn't involve lifting the timber.

Easiest option would be drilling holes;  I've read some suggesting using an 8mm drill bit. If I did do this, am I best to do one per board at the lowest point (ideally in a line to make it look not so bad!)? Or, if more than one per board, how many and how far apart? I've read warnings that such holes will expose the inside of the timber so will rot more quickly; I wondered if drilling a larger hole and inserting a grommet of some kind could offer some protection?

Another option would be shaving a few mm off the sides of the boards to provide better drainage (circular saw? router?); I do wonder, though, if this will fully clear the pooling? (This isn't something I'd be comfortable doing myself, but could look to get the builder who should be building a fence for us soon to do.)

Anyway, thanks any ideas.