First strike is nice, but it wont keep it safe past the mid-game most of the time
The main downside to Ashiok is that Wilds of Eldraine has very few cards that let the player pay life to make use of that triggered ability
Additionally, a big enough creature with Berserk slapped on it is likely to end the game in one combat step anyways
Horned Loch-Whale While certainly not a format staple, the Horned Loch-Whale is a powerful option for control decks and a key part of Greg Oranges Worlds Top 8 Bant Control Deck
Recently, Wizards of the Coast released card spoilers for Theros Beyond Death (see "Wizards of the Coast Previews 'Magic The Gathering' 'Theros Beyond Death'")
It gives you so much value for its cost, capable of accelerating you into the late game very fast, and gaining enough life to survive most aggro that tried to go under it