One thing I always check when making a deck is the curve. If you look at the curve you always want to count the number of cards you have above 4 and below 4. You should always have a higher amount of low cost cards. If you are top heavy, then you will end up conceding way too many games just because you drew bad. Imagine any deck you play against will have cards on the board by turn 4 and in some cases you will have played none.
With mage this is somewhat acceptable because it's not a fast deck. But keep in mind a 1-2 cost card can be as valuable as any 5 cost card in that it can trade early and keep you in the game. Where a 5 cost card is going to sit in your hand with the other 5 cost cards.
I can't tell you how many times I've conceded with a handful of 5-6 cost cards that do nothing.
Some cards to consider adding -
taking out -