Oxford remain in seventh place in League Two, just ahead of Crewe on goal difference, but looked on course for victory after goals from Adam Chapman and Cristian Montana cancelled out Rene Howe's opener.
Ian Morris was sent off 11 minutes from time for a second yellow card before Gulls substitute Taiwo Atieno popped up in the 90th minute to fire past the injured Ryan Clarke and claim a 2-2 draw for the visitors.
Wilder said: "I'm disappointed because we murdered a good side in the second half. We took them to the cleaners and for us to pick up just one point from two games over the Easter period against Northampton and Torquay, that we've largely dominated, is criminal really.
"We went behind from an individual mistake that the boy (Harry) Worley is disappointed with, and it was a bad second goal right at the end.
"It's something the goalkeeper would deal with 99 times out of 100. He should have just tipped it over the bar but it ends up in the back of the net."
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