As I were playing some RTS matches I noticed that hunters are pretty strong units. Their speed makes them the perfect unit for taking over strategic positions, while high firepower enables them to quickly decimate groups of lighter units. Oh, and after upgrade they can also fight aerial units. I think the cost of producing them (and time of production) should be increased.
On the other hand, devastators don't live up to their names. Yes, they firepower is high, but the rate of fire is pathetic (even after the double-fire upgrade) and the projectiles are sluggishly slow and thus inaccurate. Yes, they are quite sturdy, but they really don't have to be - they're artillery after all. Coupled with slow speed of movement and high price it makes them not cost-effective. I think they should get something boosted - be it damage per shot, rate of fire or at least projectile speed.