Board Thread:Questions and Answers/@comment-31190419-20170130180218/@comment-10733658-20170131230113

Argument #1: Ishida did not draw the body in every panel.

Ishida himself readily admits he makes mistakes, including continuity errors from chapter to chapter. Fans have observed these mistakes many times, some of which are corrected between the initial publishing and the later collected volumes. Ishida himself claims he sometimes forget which eye to draw Kaneki's eyepatch on. So I think putting too much stock in "but he didn't draw Tatara's corpse in later chapters" isn't really solid evidence. He also didn't draw Tomoe collapsed on the floor, until she was brought back into the story.

Argument #2: Dramatic Final Moment

True enough that these can be misleading. But it covers the larger picture, in showing that Tatara had been intending this as his Last Stand and has final regrets about what he didn't achieve.

Argument #3: Stated dead by others

All parties present treat him as having died. Takizawa declares that now "Aogiri is basically dead" and discusses how he dreamed of this day, when he'd kill Tatara. The infamous #2 of Aogiri is not again mentioned after that, not by any of the other parties that come charging into the scene to fight. Houji no longer considers him an active target, the Quinx do not consider him a threat, and Tomoe makes no effort to bring him with them on their only chance to escape the island. We are told 2% of Aogiri's forces survived, with no mention of Tatara having escaped.