Self printed tickets are fine if there's a live system in place to check (and kill) them to stop multiple use, or indeed fraud in that some people will accept them without scanning them (as they don't have working equipment, or are simply not bothered).
I see no reason that staff can't be given terminals that are connected to a mobile network at all times. Besides cost, but eventually I am sure this will happen and it brings many benefits.
NFC may also allow customers to download tickets to their mobile (or any smartcard) which can be scanned in the same way as any other smartcard. In fact, having a choice for the customer can only be a good thing, as long as the equipment to read/verify can cope with them all. There's equipment right now that could.