That's as good a deck as you will see in Nightmare. Can't think of anything to add to it from that clan.
Just stay with it and maybe add some damage reducers from sahkrom. Contact me if you have any other questions
Since you posted this in the Tournaments strategy forum, I'm assuming you use this for tournaments...? If so, this is probably the worst deck you can have. Most of the cards are 5/4 starred, so if you win matches, you will get the minimum amount of battle points. You should use Montana 2/3 stars in Type 1 to get maximum points. If you win a match with 4 two stars, you get more than double the battle points than if you win with 4 five stars. That way, you get about 20+ points per victory and 12+ points for a loss. I once got 19 points for a loss because I won 3 out of 4 rounds with 2 starred cards, but got beaten in the 4th round with a card with very high damage.
So far I've found Type 2 to be much better than Type 1, since the number of people playing 4 5* cards from different clans is staggering. I'd also rather lose a game with 3 points while getting in 4 games in 5 minutes (overall 65-ish points) than spend two minutes min-maxing a lost game and getting 12 points there (55-ish points).
And Nightmare might not actually be the worst. If you can fury/all pillz Kolos every time you get him even the 10 points you get per win could add up if they take 45 seconds each. What I'm seeing here that's wrong is life gain and DR. These just serve to prolong each game, and generally lose you more points than they win (Case in point, Nistarok over Mawpin is about -4 points every win and sometimes makes you wait an additional minute because of the DR).
Why don't you try something like this?
Eadh / Phyllis
Samantha / Beetenka
I know it looks a little suspect (Arawaka seems a little eh, but Milovan sees play. And she probably is awful, but she seemed like the best choice there), but it plays very fast and relies on the concept of getting at least 2 6 damage characters each round. Samantha can make a 2HKO with Kolos if you don't want to risk fury (such as 4 pill Kolos, which is pretty cool), and gives you point boosts, Beetenka may offer some additional speed. Good luck!