Group Affiliations should have included Horseman of Apocalypse…Thanks to Hervé Cousin for pointing this out.
Maestro's profile notes that he is stronger than the Hulk (Bruce Banner), though his power grid grades him slightly lower. This is because the Maestro, when first seen, in good health, and during most of his history, was stronger than the Hulk. However the power grid reflects him as he was last seen, shortly after reforming from being vaporized; when last seen he was nowhere near that powerful. Unfortunately the grids can't explain those differences. As to what power level he might be at when next he surfaces, only the writer who uses him knows.
Their first appearance was in 1980, not 1988, as noted in the bibliography.