I think there are only three sub-par songs on the album, but they are all far from meritless:
Senjutsu -
Strong right up to after the second chorus, when it starts losing it's way. The lyrics start going in circles and the music isn't particularly interesting, it also really could've done with a dynamic or tempo change as it feels a bit of a slog, though you could say it's evoking the lyric's theme of a seemingly endless battle. There are still some great moments though, Janick's solo is a ripper, the outro riff is killer and "Live to tell our sons!" is one my favourite lines from Bruce.
Lost in a Lost World -
Weakest song on the album. The verses are pretty pedestrian, the instrumental noodling goes on a bit and the pre-chorus is possibly the worst part of the whole album. However, both solos are killer, the chorus is an absolute belter and the intro and outro are nicely atmospheric.
The Time Machine -
Treads too much familiar ground to be a truly great song and there's a massive disconnect between the lyrics in the first and second halves, as though Steve gave up on the concept. I don't really care too much as the second half is tons of fun and Bruce's performance is excellent, it's like he knew the lyrics made no sense so he made sure to sell the hell out of them. Awesome solos from Jan and Dave too.