It's a little hard to judge because Pyroblast is a central card in a good Mage deck, and that's a rare. Alexstraza is a great support card for the deck, especially if you run Ice Block, but those are legendary and epic, respectively. I'll say a few things though:
1) Elven Archer. I personally would pitch this. You already have the ability to do 1 damage to things with your hero power, and while I know you can combine Archer with your hero power to kill a 2-drop, it's an EXTREMELY weak card and can't do much.
2) Ironbeak Owl. Due to Polymorph, you don't need silence as a Mage. But if you're going to use a Silence minion, use Spellbreaker. Usually silence is reserved for semi-big minions, so you rarely need to silence on turn 2, and Ironbeak dies way too easy.
3) Kobold Geomancer: Spell power can be good, but you're not really running the types of spells that benefit from it. Spell power works well on spells that do low damage; think about it this way. +1 Spell power on a 1-damage spell is a 100% damage increase; on Fireball, it's a 16% damage increase. With only 2 attack, particularly with any health buffers, a lot of players will end up killing it in the early game without you killing the mob in the process, which puts you heavily on the defensive.
4) Dalaran Mage: This card is really bad; even if you run spell power, don't use it. Ogre Magi, Azure Drake (mainly this one), and Archmage are all better.
5) Taunts. Sen'jin Shieldmasta is the best neutral taunt minion in the game. Mogu'shan Warden is pretty bad; I know it has more health, but it rarely kills anything attacking it. Sen'jin soaks up one less hit often, but against aggro decks, it kills everything that hits it. You can probably find better cards than Ironfur Grizzly, period; as a 3/3, it usually ends up trading 1:1 with 2-drops, which defeats the purpose of a taunt minion. Earthen Ring Farseer and/or Harvest Golem come to mind as good 3-drops to replace it with.
6) Darkscale Healer. I like the card; it won't end up in high-end decks, but for low-end slug-fests it might be ok. Use at your own discretion, but realize the point of this card is to heal your own minions.
7) Stormwind Champion. Your deck doesn't have a lot of cheap minions or tokens, so I don't think you'll find much use out of this card. Don't get me wrong, he's a decent card, but he works well on lots of cheap minions.
Note sure what you should replace these cards with, but I'll say right off the bat that Water Elemental is a pretty decent card. He doesn't make his way into a lot of high-end decks (though he's in my rank 3 mage deck), but particularly when you're starting out he's awesome. He pesters weapon classes pretty well by freezing their hero, and his stats are really high for a 4-drop.
Speaking of that, Acidic Swamp Ooze is a 2-drop to consider using. He's by no-means a must-have, but when you're just starting out, he probably makes the cut.
Anyway, if you want to see what high-end decks look like, you can look them up online yourself, so I'm not trying to type out a fully optimized deck for you (it would take me forever to type all that). I'm just trying to give some basic pointers.
One card I really like using is Mad Bomber. He's a common (not a basic), but when he comes down, he peppers the board with random damage. This can often be used to seed the damage required to finish something with your hero power. He takes some practice to get used to though, so you might not want to use him when you're just starting out; for example, played at the wrong time, his battlecry can lose you game, so you have to be careful when you use him. Still, he's a great card when you get the hang of him.