Never use the same deck against the same guy.
If you are referring to hrmmm and the fractal scarab deck, we lost not because the deck was similar, but because he had deflags. If he didn't have deflags, we would be able to chain dim shields and win this one. Of course that would take some Time because scarabs vs. fog shields means roughly 1 damage per scarab, and heals + druidic staff don't help either, but still 18 turns of stall is enough to kill this way. Of course it depends heavily on luck (how early he plays druidic staff, how early fractals come, are there any holes in DS chain etc.) and I guess gravity is quite useless since he will unburrow and adrenaline all his grabs only once the DS chain ends, and if he can OHKO you.
So yeah, his deck would be a great counter against simple fractal scarab, but it was a great counter against DS scarabs only because of deflags. Otherwise it would be mostly a luck based match.
Anyway, to the point. Using the same deck or a similar one is a matter of strategy. Sometimes opponents don't expect you to use the same deck, since 'it would seem too obvious that it would be countered this time' and thus you can surprise them by using the same deck. Or, for example they think you would use that deck against someone else.
Anyway, during the first war
used the same quinted spirits deck against us twice in a row (saying 'if it works, no need to fix it') and they did win both
Yeah, a poor example to show my point, but anyway the best I can think of right now.
As for the number of mistakes, I think we need to understand the mistakes we've made, so that we can do better next Time. If it was true that we didn't do any mistakes, that would mean that no matter how hard we try, we are doomed to lose, since even with few mistakes we ended on the bottom of the rankings nevertheless.
And it seems
made a big mistake in taking so many stall decks, if they all needed >30 cards to work. That seems to be the reason they had to make so many suicide decks this round, and they are 2/7, so even worse than us
And I don't understand what do you mean about darkness mark? It's mostly a matter of creatures and quints. A holy flash kills any darkness creature unless it is quinted or has increased HP (gargoyles), so darkness is immune to holy flashes only if it quints it's creatures, uses off-element creatures, or uses buffs to boost HP of their units (or use quanta denial to prevent holy flashes (doesn't work with upped ones), or if they fractal a lot of creatures).
