Recruits per Auto Play hour
Have you changed your preferred farm spot?
3 wave stages are faster than 4 wave ( see Notes )
Stronger
This
Talents
Have your heroes gotten talents like Jinx, Wound, Companion, etc.
Special skills
Have you added Attack all, attack nearb, Splash Damage heroes to your farming team.
Color stacking
Are you Color stacking double strong versus the color of the mob waves.