I don't see the big problem in turning evocation into a random 5 mana spell with DoL. People even play C'thun with DoL just for the spells
Yeah, basically this.
My list runs C'Thun, the Shattered as well, and it's basically... you either get it in your hand before you use DoL, or you don't. Your win condition can change based on what you draw and what the opponent is doing.
Some games I just go full lunacy and coin it out, followed by whatever is in my hand... some games you hold on to it and never play it because you played 3/4 C'thun pieces and want to find the last... and your opponent is very controlly so it has to be your win con.
Do we know if there will be any class legendaries in the mini-expansion? If so, you might want to wait until you see what's in that set. It could change the types of mage decks that are fun/ good/ viable.
If you intend to play standard only, id reccomnend to hold off on crafting anything untill a week after mini set it released and you can see the new meta. Something that works now can be tier 4 in a week...
If you play wild then ofc Sayge is a very good craft (though not a must) for secret mage.