It'd be 1 (or 2, with PT) less than your numbers, since a creature doesn't count himself.
This'd mean that a character with a shield can take on 3 units at once before suffering Flanking problems.
Account for the +2 AC on the shield, and that means that a character with a Shield starts being hit "as normal" when surrounded by 5 creatures. That is, a shield-user surrounded by 5 creatures is just as easy to be hit as a Greataxe user surrounded by 1.
Additionally, regardless of how much bonus to hit they have, they will still be capped by their normal methods of damage (1d4+1 or whatever). 4 damage per hit, at 100% chance to hit, is still only 4 damage per attack. Compared to not being surrounded, who'd have roughly a 50% chance of being hit, would take 2 damage per attack. Honestly, it seems pretty reasonable.
But you do make a good point. As reasonable as that sounds, +14 to hit is not.