which if I recall correctly, was 2 Voids and 12 Hydras.
Yeh but it is like sending 4 Hydralisks against 20 marines, it will not end well as you are horribly out classed as far as fire power goes.
if you had to make 3:1 ratios it wouldn't be a hard counter.
It is when not all of that 3 die. A unit that costs over twice as much resource can be expected to kill at least 1. This is not Pokémon where super effective means One Hit Kills.
Having 50% more Hydralisks than Void Rays is obviously going to fail, the army value is over twice as large as yours. I repeated your experiment and got similar results.
12 Hydras vs 8 Rays = 2 Rays dead
16 Hydras vs 8 Rays = 5 Rays dead
20 Hydras vs 8 Rays = 12 Hydras dead
20 Hydralisks is still cheaper than 8 Rays and you get to keep nearly half of them!
Yes, but you forgot the immobility of Hydralisks.
Void Ray -> 2.25 MS
Hydralisk -> 2.25 MS (2.8125 with upgrade) OFF CREEP, faster on creep
Please do not talk nonsense as Hydralisks out speed void rays. Void rays cannot retreat from Hydralisks so they are forced into combat.
you must not play a lot of HoTS, because Voids counter Stalkers and Vikings with absurd cost effectiveness.
16 Vikings totally melt 8 void rays with only 5 losses. Their cost classes are approximately equal and as little as 13 or even 12 Vikings could suffice. Upgrade those Vikings and they do even better as they gain a lot of damage with upgrades. Throw in a typical Terran land army to distract those Rays off your Vikings (since you out range them) and you will find them all blown up in no time.
For the heck of it I even got 12 Phoenixes to take on 8 Void Rays and the Phoenixes won with 4 remaining (both armies about equal cost).
Void rays are slow, expensive and easily killed. Yes they dish out pain but they better at that cost.