Errrm, why would anyone else besides the caster being making a check vs Disguise?
1) The check is involved only when attempting to mimic a specific individual.
2) Multiple checks should only come up if, for example, the caster's party is attempting to pass themselves off as a rival group of specific individuals. Yes more checks are made at +10, but all of them are going to be by the caster of the Veil spell. None of them are made by the targets of the Veil spell so far as I can read. It all references "you".
3) Yes that brings a rather odd state of affairs where the party's skill monkey in Disguise may be worse off having the not so Disguise skilled wizard (typically) using Veil on him.
