Re: DC's New 52: Reviews and Discussion (Spoilers welcolme and likely)
His overeagerness to kill has been something that has and continues to be explored in "Batman and Robin"...having not read the issue though I can't really comment as to why he was off. Perhaps it was just the writer not really writing him "right" which has happened on occasion when Damian has appeared in other books.
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Ignoring the The Last Stand since 2011.