To be honest, I'm not sure it's a saviour complex. I think it's rather that Takanashi has seen the "reality" of dreams and feels the only thing he can do as a teacher is to ensure his pupils have all the information they need to make an optimal decision. Given that they're teenagers, of course information isn't the only thing they need, as they also lack the emotional maturity to process that information adequately, so the second visit when their dream is crashing down gives them the opportunity to do that.
And that's not to save them, I feel it's like how he can save himself. I'm not sure how altruistic he is. His behaviour verges on a monomania, but that could be said about the train engineer and the voice actor arcs, too, I don't see this as more extreme than the previous ones. In a sense, he could even be described as a sort of stalker for monitoring the first few years of his former charges' adult lives.
Then again, this is being played as Takanashi being able to see through the insanity of the world that creates situations like those his former pupils are living. This series in a sense is an indictment of society. I'm positively surprised at how non-judgemental the series is of the students in each arc, even Ryo. And frankly, series can be guilty of far worse things than that, I'm okay with it.
