Since I pulled an Evolutionary Apex and I wanted to take a crack at the Grandmaster I decided to put my post-UP Spirit into this deck. It's fairly unrefined, since I don't play a huge amount of games per day, but it's 3-1 at the start of Diamond so it might be worth looking into. My one loss was to a Vet that was holding onto Nosh-Rak when I Apex'd, which honestly was just hilarious.
The deck is basically just "Play as many giant things as possible and pressure your opponent to constantly answer increasingly powerful threats". It has no T1 play unless you hit Flash, but that's ok. As weird as it is to say, you can generally ignore T1 since everything you play down is such a giant threat by itself that you can quickly wear opponents out without consuming too many resources of your own. You have tempo tools in the usual Lavaslasher/Makantor, and Thunderhorn also causes a lot of headaches and usually forces difficult plays to remove.
Since you usually aren't playing more than 1 card per turn, your hand tends to remain quite full late into the game. That's where Evolutionary Apex comes in - your goal is to keep 3-4 powerful threats in hand to super-cheat them all out and force an all-out war. Most opponents will be exhausting their hand during the game to put down minions and remove your own, so you don't tend to give that many minions to your opponent. If you do you have Thunderhorn to take advantage of them. If you have a Makantor in hand when you Apex it gets thrown out with Rush as per usual (though its spawn is random so it may not hit much). Tectonic Spikes is there as a refresh option for after you use Apex, as it almost always cleans your hand out.
The nice thing about this deck is that even if your opponent does have 2-3 minions that get placed with Apex, they are usually lower-quality than your own ones since your curve is irresponsibly high. If they do have that many minions to throw down it usually cripples their next turn, as you basically drain their hand of every card and their minions can't generally kill yours.
It's worth noting that I have not cast an especially high-value Apex in all of the games I played with this deck. It's obviously important to get, but it's definitely possible to simply out-value your opponent before even getting to play it. This is where Earth Sphere tends to come in, keeping you in the game whilst you pick and choose your heavy hitters.
Some other notes on specific card choices:
Vaath over Starhorn for two reasons - You don't want to give your opponents more cards to proc Apex with, and Vaath's BBS adds to the pressure generated by this deck. Due to the low number of cards played during most turns, you'll want to BBS often so you can make the best use of your Mana, and Seeking Eye would be a bad BBS to spam in most matches.
Terradon is here because the 8 HP is a giant roadblock early game. Only 2 copies due to space.
Komodo Charger is great for this deck since Apex doesn't proc Opening Gambits, which means it tutors out your 5/6 with no cost. If you do have to play it earlier it's still ok, as it synergises well with Thunderhorn and Makantor.
No Drogon due to space. I'd love to have it, and it would go great with Apex on 8 Mana, but Sunsteel/Thunderhorn are better 4-drops so it doesn't make the cut.
No Keeper of the Vale looks weird, but Keeper is a terrible card to have in hand when you play Apex. You don't trigger OG's when you force minions on the board like that, so it becomes a horribly weak 3/4 that often clogs up your hand. Great for its own archetype, terrible for this style of deck.
Silithar Elder is partly because I only have 2 Grandmaster and didn't want to have 3 Juggernauts, but the slightly lower Mana cost and Rebirth do give it some advantages. This could be replaced with EMP if you're worried about value generators.
Other options would include Elucidator for more Rush, Blood Taura for the giant body, and Meltdown to try and pick off a Big Bad that the opponent got off of Apex. You could cut back on some spells for these, but I feel like all of them are necessary.