D&DNext, as it is, is realy simple, the concentration rule is one of the more easy to use rules around the table, having damage interrupt it is also quite logical, also trying to use an heavy crossbow or a long spear on some who stand right next to you is hard and it's also logical.
Evidence. please? It may sound logical, but then a lot of people thing a greatsword should be hard to use in a 5' passage. And they're wrong.