General

Against aggro you have the full set of Mage actions.
Your game plan is to survive and not take too much damage. If you do, you will win anyway.
If you lose to aggro often, pick up more Prophecies and Heal/Drain. As you can see, in the current version it is quite greedy on that one, but remember that Echo can give you Drain/Guard/Charge/Lethal.

Against control you have the full set of late game Mage cards and can snowball with Echo/Praetorian.
You will win against Control Decks that don’t have that.

Break runes only if you have an answer on the board or the hand.
Even falling behind in cards can lose you the game.

This is a very versatile Deck and good substitutions and alternatives do exist. I encourage you to experiment and share your experience. Just read along.

Cards

Execute
Hard counter against strong cards like Daggerfall Mage, which is very common.

Firebolt
Counter to low hp snow ball cards.

Shrieking Harpy
Good against aggro or any creature that sets up value in the shadow lane and can be key against Pilfer or Slay cards.

Wardcrafter
Solid against aggro and can create insane value by warding Daggerfall Mage or high cost minions.

Crushing Blow
Cut by a lot of players, but the potential to play around Cover or Guard, especially on early turns, is insane.

Cloudrest Illusionist
Good body for a Prophecy and can setup great value for trading or Execute.

Vicious Dreugh
Can be substistuted, but it is great against Hist Grove and Support centered Decks and has a solid body.

Knight of the Hour
Cut by some players, but I think the Heal/Guard/Prophecy is just great.

Lydia
New in the expansion and has insane stats and a great effect. Remember that she can be attacked by both lanes.

Praetorian Commander
Buffs all creatures in your Deck by +2/+2.

Echo of Akatosh
Buffs all creatures in your Deck with a random Keyword.
If you play the card once, I think Praetorian is better, because +2/+2 has more impact than one RNG keyword, which can be a useless Breakthrough/Regenerate, but if you play Echo 2/3/more times the chance is pretty high that you get Drain/Ward/Charge and Drain is absolutely crucial to survive.
Echo has a better body than Praetorian though.
I’m not sure what the best composition is, yet, I am still experimenting.
You might play +1 Echo, +3 Dark Rebirth and -2 Praetorians to maximize your Echo procs, but Praetorians transform your small creatures into real monsters, while with Echos you have to be lucky they gain Lethal and Ward.
Overall I’d say that these cards are a good addition to the classic Control deck, but should not be overused, because Aggro kills you.

Winterhold Illusionist
A blink. It resummons a creature, so their Summon effect triggers again.
This card is insane with any of your 6+ cost creatures.
Against aggro, you can also resummon a Harpy or heal a big Guard.
Alternatively or additionaly, you can add Dark Rebirth, which is an action that does the same.
The reason I only picked the Illusionist is because for 2 more man it comes with a 3/3 body and can be buffed by Echo/Praetorian.

Ice Storm
Damn solid card that often wins games alone against Aggro.
I include 3 copies to maximize the probability to draw it.
Also a great counter versus Haunting Spirits.
It’s not bad versus Control either if you use it right. Also, it counters Atromancer.

Supreme Atromancer
It summons 3 dangerous tokens for 9 Mana and is a great finisher.
Could be subbed with Ancano.

Mantikora
With Praetorians and Echos you will win against other Control Decks, so I think 2 copies are enough.

Miraak
Is still great and blinking him in the late game is just insane.

Odahviing
Same as Miraak.

Comments on Alternatives

Pillaging Tribune
I ran this card before the patch. It has a good body and the instant Drain effect can safe games.

Ravenous Hunger
Great counter to shadow lane aggro and Drain.

Camlorn Sentinel
I ran this a few months ago instead of Wardcrafter.
It’s basically the same body if the Warcrafter warded himself, BUT has Prophecy, which is better against Aggro.
It just does not have the same value/surprise potential as a Wardcrafter warding Daggerfall Mages or high cost minions.

Undying Dragon
The body with Drain is great, even without the +5/+5 effect.
It’s like the yellow Night Shadow.
Usually, we want to play Echo/Praetorian on 6 Mana, but since Health is often an issue, you might just try this.

Dark Rebirth
You can experiment with the amount of Blink cards, but too many can be quite greedy/clunky/slow.
Again, this is a classic Control Mage with the small addition of Blink/Echo.
I tried pure Blink/Echo/Prophecy Decks, but the win rate was just terrible compared to the more diverse approach.

Loyal Housecarl
Prophecy with Guard is always good, but I prefer the Heal from Knight of the Hour.
If you need more Prophecies against Aggro, take it instead of greedier/more situational cards.

Ancano
Basically a Shocking Wamasu on steroids. I think it’s overhyped, but it might be a good replacement for the second Atromancer.

Elusive Schemer
It’s great for card draw and putting free stuff on the board, but I feel like this is not the problem in the current Meta.

Shimmerene Peddler
Some Mages like it, but I don’t in this Deck.

Fate Weaver
It’s a good Prophecy and card draw, but often ends up doing nothing against Aggro.

Paarthurnax
It’s a good late game card, especially if you RNG Soul Tear, but I think for this Deck there are better cards.

Thief of Dreams
Solid card, but slow, just like College, we have better alternatives to get value and go crazy.

College of Winterhold
I think this card is way too slow. We have great late game cards and snowball potential, we don’t need cheap RNG spells.

Chanter of Akatosh
The currently included actions don’t fit the creatures mana cost at all and I think this card is way too greedy and too different from the game plan.

Cunning Ally
Earlier it was a staple in Control Mage, but I began to hate it, because it was so unreliable.
Especially in this patch, I think there are better cards.

Bruma Profiteer
Solid body, but I think the Heal effect is not that significant, since we don’t play too many minions.

Dawnstar Healer
Some include this, but I myself don’t like breaking runes till the end.

Grisly Gourmet
I think Execute is enough. It’s cheaper and has better synergy with Cloudrest and Ayrenn.

Dark Harvester
Knight of the Hour just feels better, but if you want to pick up more defensive stuff, it’s an option.

Thieves Guild Shadowfoot
Stealing a card is great and being able to dodge a Prophecy is great as well, but I think it fits better in non-control Decks.
Also it’s pretty weak against Aggro, which is a bigger problem than Control.

Mystic Dragon
I don’t think it fits in here. We prefer defensive Prophecies here.

Fire Breath
I think it’s too slow. We have way better alternatives and don’t focus on Shouts.

Call of Valor
Does not fit in an Echo Deck.

Alduin and more Dragons
Alduin Dragon Control Mage definitely works, I play one as well, but that is a different Deck.