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.
I've only faced 1 resolved Gaea's so far, the mill can see to the sufficient disruption (and counterspells for relevant fetch spells) and there was an answer already on the board. I was down to 7 life and he swung his hasted Gaea right into
Disciple of The Ring, and since I couldn't spend my mana on a counter spell due to Gaea's text, I pumped five into Disciple to make it 8/9. This is why Disciple is such fantastic value as apart from Kothophed, she can be pumped with the entirety of your deck if needs be. If the board is clear and the win is obvious (or you suspect no Gaea's) then swing away, but it's better to stay untapped and act as a response. I've since ditched
Maw of Hell as this didn't answer Gaea's and that's the main "big bad" I can see being an issue.
I have already faced a good counter deck, and constructed it myself. Specifically a playset of (forget the name) that 3 mana 3/1 black elf who forces you to discard. Leave it and that's 3 damage a turn, kill it and you waste 2 cards. Multiple of these would cripple you enough early, and the re animator strategy/resolved
Evolutionary Leap also counters this well.
Erebos's titan also plays hell with you since lacking creatures makes him automatically indestructible. So I'm aware that non-elf Golgari decks are the flat counter to control, but atm the elf variant/aura/aggro and thoptor decks are far more common and easy to deal with.