If you post a deck, people will be happy to give constructive criticism.
If there isn't a deck problem, it's hard to say what you're doing wrong. It's just simply that the top players, on average, will make good decisions more often than you will.
The better players have a certain 'awareness' in game that others don't, and it's something that is developed through their experience.
As JO3 says, there's really no advice people can give you aside form the obvious. To break into 1400e will take a little bit of everything including: experience, luck, skill, determination, and patience.
There's no magical formula to it, some people are simply better at reading others.
Post the decks you're using and we'll see if there are any changes that might help.
Edd does indeed have merit against Nightmare, but I don't like how his courage makes him a big DR magnet. If Nightmare is your reason for picking Edd over Desmond, Gianfranco does the same dropping 1 damage for 1 star.
Also if you take a look at the Nightmare half you're using, you'll see the benefit of Desmond against them. Edd isn't bad, but Desmond is my first preference.
Angelo is better than Prince Jr in my opinion. If you're winning enough rounds for the 1 damage to matter, you're winning with the wrong characters too often.