Only counts vintage-legal cards.

"Most text" refers to the number of characters in its rules text, with the typical encoding of symbols. (e.g. the green mana symbol is three characters, "{G}".) Illusionary Mask has 657 characters.Only individual parts of multi-part cards are counted. (e.g. only one face of a DFC.)

In the event that Dance of the Dead is errataed to have less text, causing it to fall beneath some other card, that will be sufficient to resolve this market to YES.