1. It's too big. Those two hourglasses won't help in a 50 card deck, since you probably won't draw them in time anyway. I would suggest making it 30-40 cards if you want to get the cards you need before the opponent kills you.
2. You should focus on one or two strategies. Don't just cram a bunch of cards into a deck. Pick something you want the deck to do and just go with that. Here, you have all kinds of stuff: Otyughs, Vultures, and Boneyards (which don't work that well together), Ghosts and a dragon (for offense, I'm guessing), and some random Darkness cards. You're just putting a bunch of cards that don't have anything to do with each other in a deck. That won't work well.
3. You said it works well for opponents with lots of monsters. Which kinds of opponents? Do you use it for AIs, arena, or PvP? You can change it to work better against a specific opponent. Also, how does it work well against lots of monsters? I only see 2 cards that could eat monsters. Those Otyughs probably won't be able to eat everything an opponent throws at you.
So basically, you need to make it smaller, take out some useless cards, and focus on one strategy.
Here's a sample deck focusing on Otyughs:
It works alright against AI3, but it's not very good. See if you can make a better one!
