Well exiles is about discarding cards, you could definitely combo that with maybe cards that trigger effects whenever someone discards cards (if they made any). Sleepers obviously counters that, but the more cards you make that benefit you more than sleepers then it would just make that a soft counter more and more.
Right now, Exiles mechanic wise focuses more on discarding your own cards so I mean. Even with sleepers and all I guess the faction was just supposed to benefit more from people discarding cards than the opponent.
I forgot to make my own entry so I guess Ill make one now:
The Pale Forest
Whenever a character enters play from the graveyard, it moves to the Assault Zone and gains +2/+0. At the end of the turn, it gets -0/-4 permanently.
Exiled characters actually count as returning from the grave somehow. Can be used for a burnout aggro exiles type play, or counter sleepers somewhat, assuming you can survive the initial surge. Zombies get permanently debuffed, so even if they return from the grave, they die immediately. Can be used with mass death if you can predict hekheem.