Don't you need some way to protect the Willbreaker? Maybe Disciple of the Ring for untap and another way to take creatures?

Into the Maw of Hell kills just about everything in the format, even a Renowned Colossus. Plus it hits problematic lands like Rogue's Passage or the Foundry. You should be able to play a copy in most red control lists.

I can't offer suggestions yet, I'm working on the game right now. I was just pointing out that one copy of Into the Maw would be something to think about during your testing.

I am always interested in Grixis Control "just because" so expect me to try and build one soonish. We can share ideas then.

Bounceburnbuff- I think creatureless mill has the potential to be strong in this format, and Grixis seems like an obvious choice. The problem with slow win conditions is that it guarantees you will see everything your opponent has, and even if you can answer 95% of their deck that 5% you can't answer can kill you.

Gaea's revenge is a problem for your deck. I am not sure how often we will see it. I would expect Grixis to perform maybe a bit better than Jeskai against creatures, but it has very few answers to resolved artifacts enchantments (disperse x2 PLUS countermand x4), and white does better vs. Revenge.

Both jeskai and grixis have answers to gaea's revenge with celestial flare and fleshbag marauder. Jeskai wins out only due to tragic arrogance being better than languish in that scenario. From what have seen from the last 2 days on the ladder is no one has played gaea's revenge though. Most are going for 2-5 cmc drops very few people have played bombs at six mana or higher Kothophed, Soul Hoarder and Alhammerret, High Arbiter have only shown up about 2 times each. If this trend continues (personal experience only not sure what others are running into) I wouldn't worry about bombs too much atm and might even change my decks a bit if the meta remains this way.

Here's my take on Grixis control where mill is the primary win condition. I pack enough board control and counters to keep off what I need, and use Disciple of the Ring as a secondary wincon/extra control. Against aggro matchups (particularly mono red) this setup has had few problems, unless I face a mono white enchant deck that quickly gets out of most of the 4 damage reach (the reason I pack Disperse).

Grixis Mill/Control (60):

1 Mana -
4 x Fiery Impulse

2 Mana -
1 x Jace, Vryn's Prodigy
3 x Telling Time
2 x Disperse
4 x Twin Bolt
4 x Reave Soul

3 Mana -
2 x Sphinx's Tutelage
2 x Exquisite Firecraft

4 Mana -
3 x Inspitation
4 x Countermand
4 x Bone to Ash
2 x Languish

5 Mana -
1 x Disciple of the Ring

Land -
2 x Sulfur Falls
2 x Drowned Catacombs
2 x Dragonskull Summit
2 x Dimir Guildgate
1 x Rakdos Guildgate
6 x Island
5 x Swamp
4 x Mountain

Mana Curve:
4 - 14 - 3 - 13 - 1

The lack of answers to big creatures in this format is simple. There's basically none. Woodland Bellower,Outland Colossus and Kothophed all take too long to hit the board for me to not have a counter spell ready or a double spell masteried Fiery Impulse/ Fiery Impulse + Exquisite Firecraft. I'm assuming the WotC will be adding more "big stuff" with the Battle for Zendikar expansion once released, because atm there's nothing common or big enough in the toughness department to counter this deck. There's plenty of high power, but not much with above 4 toughness to worry about.

I'd like to add Perilous Myr in here somewhere, but I haven't found it's presence needed with all of the early removal available. Jace does feel like a dead card a lot of the time and might be better off in a specific mill deck, but his +1 has saved me on occasion. Lastly, I take Telling Time over Read the Bones as it essentially gives you the same card draw (top of library is good enough 90% of the time), it's instant speed, I don't lose 2 life and I can still dump 1 dud card when looking 3 cards deep.

I made my deck very similiar but cut Exquisite Firecraft due to double red and added Fleshbag Marauder as a better out to stuff this deck cant deal with and it works pretty good since it's a sacrifice effect and board generally clear anyways. So, -1 Jace -2 Firecrafts +3 Fleshbags. Btw Erebos Titan is a huge silver bullet due to the "invulnerable due to no creatures" clause.