>>282926518
The biggest "issue" is that Mahou is a weak, undercooked season that masks its weaknesses through the inherent strength of having just 2 girls + the eventual useless 3rd wheel (notice that this marks a dip in the show's quality since now it has to support 3 heroines).
All 2-cure seasons are at least "decent" because they don't have the additional baggage of tons of other characters to deal with, give screen time to, develop, etc. You can actually "solve" several bad seasons' main problems simply by deleting characters or consolidating their traits down into others until you have a duo, and suddenly the show is much more watchable.