Minecraft wiki entry for Development_versions, associated text: "Johnny" vindicators are now also created by setting a new byte tag, Johnny, to true, in addition to renaming the vindicator to Johnny. The tag supersedes the name, so a Johnny tag set to 1b will allow arbitrary names with the "Johnny" behavior, or a Johnny tag set to 0b will allow the name Johnny without the "Johnny" behavior.
Their axe is now one of their HandItems, whereas before it was purely a visual effect. This means their attack now disables Shields.
Vindicators have been heavily buffed - their attack damage on Easy has been increased from 3 to 7, on Normal 5 to 13 × 6.5, and on Hard 7 to 19 × 9.5.