honestly, I think your getting bad advice from a lot of people here and your looking at overbuilding your wheels. You said CREDIT CARD TOURING. You also didn't say how much you weight. IF your well into clydesdale territory than what people are suggesting is valid but if your well south of 200lbs, you don't need anything nearly as stout as what people are suggesting. 32 holes will do you fine and you don't need the added width that some touring rims like an A719 have. IF you know your only going to be riding on paved roads and on 28c tires, you could simply build up 32 spokes front and rear and I'd go with double butted spokes and use a rim like a velocity fusion or deep v. I'm all for durability but there is apoint for certain people where things are overkill.

REgarding shimano hubs, the MTB hubs are probably better sealed to keep dirt and grime out of the bearings and as others mentioned, the dishing issue will make a strong wheel. Not a huge deal if you are credit card touring.