After having beaten all the NPCs and acquiring all of there cards, I can honestly say the only truly hard NPC was Swift because of his high powered deck + chaos.

On an off tangent, Marcette also was difficult initially but she is subject to regional rules daily so that makes her infinitely easier when plus or same come in even with chaos in play.

Never understood peoples struggle with Rowena or other Random users. Those NPCs felt way easier after I unlocked the 2* deck. Guess not everyone was that good at TT.