I think a horde mode could work in Evolve would be like an arena. The monster player could come in as each monster after so many waves of minions. After a certain amount of waves comes in as goliath then Kraken etc. Only thing i could see that would be a problem is only being Goliath minions, So maybe wildlife come in on waves too and attack hunters. Or make kraken and Wraith and Behemoth minions for this mode and Defend.
Just linking these for reference in this one. ^.^