Took my Exos 46 out for the first time last week and had a couple of niggles, enough to make me give the pack a really thorough inspection on my return. That's when I noticed that there are absolutely no drainage holes for the main compartment of the sack; if water gets in it's going to stay there until it can seep out through stitch holes. Surely that can't be right? Is my pack missing them? Even the side mesh pockets have a drainage hole, and they can only hold half an inch of water anyway!
(Incidentally, the niggles I had in use was that the damned pole-stow thing on the strap nearly rubbed a hole through the sleeve of a brand new £50 shirt - and it appears there's no way to remove it - and stowing Source Liquitainers in the side mesh pockets neatly sliced through several threads of the mesh, and that before I had even picked the loaded pack up!)
Looks like you didn't enjoy your experience! For what it's worth I've had one since near the beginning of the year and I get along fine with it! (Though I never use the pole widget!)
No "drainage" in my main compartment, but there's none in any of the other of my packs (& I own quite a few for some reason! Might have to sell some!) Surely if you have the lid down the pack isn't exactly going to exactly fill up with water?
(Incidentally, the niggles I had in use was that the damned pole-stow thing on the strap nearly rubbed a hole through the sleeve of a brand new £50 shirt - and it appears there's no way to remove it
A quick snip! maybe.
If you can bear to take the scissors to your new pack , If you want drainage holes maybe a cobbler or tailor could punch a couple of grommets into the bottom of the main compartment for you.
Both my Osprey Talon packs have one central riveted drainage hole in the bottom of the main compartment - I presumed all Osprey packs would be the same.
Actually, I was more than happy with the pack - a superb carry, which as an ex-Atmos and current Talon user I was expecting anyway - and I think I have located the precise perpetrator of the sleeve rubbing: not the pole-stow toggle and the plasticky fabric that goes over it, but the bit of clear plastic tubing around the shock-cord . I'd left this as it came, flapping around a bit, and its edge is surprisingly sharp and abrasive. I have now cinched it down as far as it will go, so it forms a neat inverted 'U', so hopefully that's sorted it. (I would happily take scissors to a feature I'm not going to use, but in this case it would be a bit messy because it would expose the unfinished and unstitched end of the strap that affixes the buckle - if you look under the pole-stow toggle you'll see what I mean).
The flappy bit for the pole carrier I pull upwards and take a double turn around the plastic bit at the end of the chest strap underneath the gell pooch, seems to keep it out of the way nicely!
The reason that the Talon has a drain hole in the backpanel is that all Talon packs have an externally accessed hydration sleeve that sits against the back. This sleeve is open at the top, so if rain comes in it has somewhere to go (not into the main pack) but also if the bladder leaks, again it doesn't go into the main pack. the fabric between the hydration sleeve and the main compartment is waterproof.
The Exos has an internal hydration sleeve so it doesn't need this feature.
, If you want drainage holes maybe a cobbler or tailor could punch a couple of grommets into the bottom of the main compartment for you. 
