(I was surprised that after my 12 Chain Lightnings, only 8 of them remained. Then Armageddon with 1000+ damage and another Chain Lightning with 1400+ hit them, and they didn't even flinch, even though they had no resistance at all:confused:)
They resisted both times because they were standing next to unique units – this is a unique unit ability. Although 2 resistances in a row is a bit much, but it's my fault – they should have taken the first Chain Lightning, not the Storms.