The moment you know that fusion gaia can destroy card during either player turn without backrow, this is expected to happen.
Backrow is intended to disrupt combo in the first place. Trunade doesn't work when we started to leave backrow
The point of the OP is that the tournament has a side deck. The winner of the tournament basically said Necrovalley won him a lot of duel. So go on play it in ladder with but you have to main deck necrovally to beat other deck because the real game we Play has no side deck in it.
No, many decks has 2/3 MST maindeck, so necrovalley is not a autowin card. It's strong but not autowin (shiranui has balista, onomat has 4/5 cards to out necro). Grucius won because he is lucky AF, like ALWAYS the right card in hand. Borderline cheating.