Road levers like that have a lot more flex than a decent mtb lever so you end up using part of your brake pull simply flexing the lever. This means that you have less effective cable travel and you end up having to set your BB7 pads very close to the disc. That gives a high likelihood of rub because you also have compression in your outer cable to deal with. You do need the road BB7s with 105s.
You can compensate for the lost travel by using top grade outer cable which compresses less (Nokon etc), or use something like Avid Full Metal Jacket (steel tube for part of the outer run).
I take a DIY approach and use aluminium tubing to replace the outer and only use ordinary outer for the bits where it has to flex. This has the virtue of being cheap. 🙂
Doing this improves the brake to where it is as good as with mtb levers.