Of course, we cannot completely rule out the theory that Derevenko shamelessly abandonned Aleksei, but we only have Anya Virubova's word for it...so until we find more evidence, we cannot say for sure that he was a traitor. After all, he asked to come back. Some say that it was to use the Imperial Family's situation for his own interests, but what if he really had to take care of his family, and after making sure that everything was okay, tried to come back to his duties for the Tsesarevich?
Romanovy: ventsenosnaya semya has shown both Derevenko and Nagorny, which is I think a première; you see more of Derevenko (especially with the boxing lesson, and with the Fabergé egg), and some of Nagorny (in Tobolsk and helping Aleksei off the train in Ekaterinburg).