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6rm 6rm 6rm 6rm 6rm 6rm 6rt 6rt 6rt 6rt 6rt 6rt 74a 74a 74a 74a 74a 7q0 7q0 7q0 7q0 7q0 7q0 7q0 7q0 7qd 7qd 7qd 7qd 7qd 8pl
Number of cards in common (not counting the pillars = 4! I just don't get your comparison. If you look around you'll find more than one deck with 4 cards commune with Splat which are not as efficient. You could also say, why not simply use Splat? Also I suppose you realise that the rare present in the two decks are just all different. For a lot of people rares is the main reason why they don't use Splat ...
Splat might be better but the core strategy is completely different. Nightmare and RoL are creating a field-lock with solar buckler which is completely absent from Splat. Also Filling the hand of your opponent with cards he can play combined with neurotoxin is also never seen elsewhere.