Powerslave's 'fillers' compared to NPFTD, FOTD, DOD fillers, are gemstones. Diamonds! Powerslave's only minor problem is: two songs about the same topic. As a composition The Duellists is perfect.
I don't think NPFTD has fillers - all songs are well balanced and more or less are on the same level (the title track is one of the band's best songs imo). The same is with Killers. And if I have to give another similar example, this will be TXF - all songs are important for the album's mood and message and there are no bad songs imo.
About DOD, I like all songs without ''Age Of Innocence''. Maybe only ''New Frontier'' can be viewed as a filler, because it's Nicko's only writing credit for the band. Janick has 3 writing credits, but for the previous album he has 4, so I can't view ''Gates Of Tomorrow'' as a filler. Yeah, if you remove these songs from the album, the album still will be great, but I can't call them fillers. With this album, the band did some experimentations with the songs and I think that was intentional.
Agree about ''The Duellists'' and two songs about the same topic.