Even if the rack wasn't shaded, the sun is really the least of your concerns when parking at a bike rack.
You don't mention what's providing the shade. If it's shaded by trees, fallen branches, dripping sap, and bird droppings will all be a concern. If it's shaded by a man-made structure, you might still have bird droppings. If you do, it'll be a lot.
As far as weather concerns go, precipitation is a bigger concern. Even if's covered, the wind will blow bad weather in. Water is, of course, hard on bikes.
Locking your bike up and taking it off of a rack is harder on it than you might expect. You'll end up scratching and dinging up the paint when you rest it against the rack, as well as locking and unlocking it. Since you'll likely attach the lock the same way in the same spot, it'll also rub off the paint where it contacts the bike over time. You can alleviate some of this by being super careful, perhaps carrying a towel or something to use as padding. But accidents will eventually happen.
Unfortunately, no matter how careful you are, some of your fellow commuters inevitably won't be. If the rack ever fills up, people will be trying to squeeze their bikes in, bumping and scraping every bike around them, yours included.
Finally, thieves will be a large concern as well. If they're looking at a rack and your bike costs 5-10 times as much as any other bike at the rack, which one do you think they'll steal?
If you're absolutely insistent on spending a chunk of change on your commuter, get one with a boring paint job, a belt drive, and an internally geared hub (or a single speed, if doable in your area). The belt drive and internally geared hub will alleviate some of the precipitation concerns, but not all. The boring paint job will make your fancy bike less obvious to thieves. You'll still get plenty of scratches and dings from the rack and other commuters. You'll still have precipitation concerns with other moving parts. And bike thieves might still steal it.
Alternatively, get a beater bike and don't worry about any of that stuff too much.