I've always thought Applejack's deck was somewhat weak, or at least 'wanting'.
The Stubborn ability is only useful if you can exhaust a card to attain some sort of ability from doing so.
However, there are other options!
If you can load the deck with 3 copies of Sunny Smiles, Iconic Friend, there can be some interesting synergy going on here!
All you need to do is force your opponent to discard cards!
Load up with Yellow Parasprite Troublemakers.
Throw in a Drill Bit, Destruction Worker,
And maybe one of two Applejack, Plant Leader
Every one of these cards feeds Sunshine Smiles, Iconic Friend, either singly or collectively.
And after all this, if you want to add insult to injury, throw in Apple Cider at the right time to stop your opponent from scoring bonus points either on being the first to resolve a problem or winning a faceoff.