Well, I stand corrected. If you dump upgrades into archers you CAN spam them up and beat hard levels. Hrm. Not nearly as fun though, but it IS an exploit.
I think anyone touting archer spam or complaining about speed hasn't played through anything but the early levels or is happy playing on easy or normal with minimum mission scores. If you play missions on hard, you won't be archer spamming or complaining about the slow speed.
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