D2 Hydra playstyle is even boring. Having fire immunity made Hydra build even less appealing.
D3 is the one that expanding D2 Hydra playstyle further here so if D4 wants to expand hydra playstyle, D3 is where they should look at.
Hydra can shoot high speed elemental attack and freeze enemies > hydra can shoot slow fire ball.
And if they allow you to summon more than 6 hydras, it is obviously it will be weaker than D3 Hydra. You need to take that into account.
Quantity or Quality?
The problem with Hydras is thereās no control of target-fire so yes itās a support spellā¦ See that Zombie that is Cold-Res in the Bunch ?, attack it, nope, imma puke all my firebolt shots on the Fallen Shaman that is Fire Immune 
TBH I donāt care, Hydras are a nice niche stuff that can make game look more interesting at times but probably not the best damaging optionā¦ The SAFEST of all them, thatās for sure, but probably not most effective though
Now, what the limitation should be ?, if I remember correctly in D2 the limitation to Hydras was their duration, they last relatively short (like 3-4 seconds maybe ?) and higher levels it lasts longer (not sure if in tooltips but think thatās how it worked)
Think the duration limit isnāt a bad route, but again, what the heck, might as well just have a Firewall or Meteor that will probably damage stuff/groups in a more reliable fashionā¦ As for D3 ?, think it lasted a freakinā long time and blasted everything in itās path (i.e. much higher damage output) but could only spawn one at a timeā¦ I guess that reduces the āfine tuningā option, i.e. do I want just 2 or 5 here (if your one does damage like 5 then all you can do is cast ā5 at a timeā)
Regardless, itās a nice/fun skill, but donāt think itās something that changes the outcome/immersion too much though, itās kinda easi to balance - allow more hydras ?, reduce damage output, limit more hydras ?, increase damage outputā¦ 
Thatās fine, however I myself am mostly done for now on that matter.
Been there did that and honestly it doesnāt do much.
As i said in my initial post statement, i play diablo for fun, to me casting one hydra is not fun, itās restrictive and boring, i would rather have an army of them littering the battlefield, i am all for excepting they will never be as good or as strong as one big one, but thatās why you have other massive casts for.
As mobs being immune to fire attacks thatās a d2 issue and i doubt that will even be a problem in d4.
Quantity or quality, how about smack in the middle with Balance.
allow 4 hydras, with rare items that allow us to cast 2 at once and also perhaps increase the number of hydras to 5.
Like i said, having the weapon in diablo 3 that allows you to cast an extra hydra is a retarded game system, it should be based on mana, the more mana you get from better gear the more you get to cast more of spells. its Progression of power in my eyes.
As a sorc if i decide to pump all my points into int and have a massive manapool and can cast 6-7 hydras why not, at the same time i decide to pump all my stats into something else, to make a funky build with strength, i can only make 3.
They want us to have unique builds, the system of only having one hydra is not unique or more importantly is less fun, at least to me.
And I play Diablo for fun and I donāt like casting a bunch of useless things if they canāt kill anything on their own especially in the game that battle doesnāt even last more than 5 seconds when you are farming.
Nope, having a legendary weapon to cast extra powerful hydra is infinitely better than having to recast 4 hydrae to achieve maximum damage every time you see a monster. It made farming with hydra build is so inefficient and slow.
Able to cast extra hydra and later allow these hydrae to freeze the enemy is a progression of power.
You judge on the game that you donāt even know anything about it. How about you stop using your D2 standard to judge D4 Sorc or Hydra? There must be a good reason why they gave the 20s cooldown for the Hydra, and maybe there will be a legendary item that will remove the cooldown or something from the skill tree or rune or passive or willpower will enhance or change the D4 hydra gameplay.
Itās called a discussion,
hydras were absolutely crap in d3 until hey made a massive 6 piece set for it, regardless of what you think, casting 1 hydra absolutely sucks.
In the future they can balance the game better, do you like going from rift 50 to 100 in the blink of the eye just because you found a 6 piece bonus, i donāt, nor do i like the +4000% damage bonus from diablo3.
Things need to change for the better, hydra needs to be improved.
As for this remark
You judge on the game that you donāt even know anything about it. How about you stop using your D2 standard to judge D4 Sorc or Hydra? There must be a good reason why they gave the 20s cooldown for the Hydra, and maybe there will be a legendary item that will remove the cooldown or something from the skill tree or rune or passive or willpower will enhance or change the D4 hydra gameplay.
I trust the development team not to mess up my favorite spell going from d2-d3, they messed it up, i am not going to sit here and hope they make the right design choices again, i have thousands of hours in both diablo2 and 3, i have waited enough.
If youāre happy with their systems then thatās good for you, i like the direction diablo4 is going but i am not giving them blind faith as i did in the past.
If you are, then good for you, there is a reason why diablo3 is dead at present.
What discussion? All I have seen so far from you is this spell sucks because it donāt do what I wanted.
And it doesnāt change that D3 Hydra that empowered by legendary items and sets are absolutely fun and powerful to use. And casting 1 hydra that has 5 lesser hydra DPS combined is better than casting 5 hydrae that deal the same combined damage as 1 powerful hydra. It makes a great difference when you are farming in the late game.
Irrelevant to hydra discussion and gameplay.
D3 hydra is an improvement over D2 hydra, so Blizzard is on the right track.
I like D3 Hydra because it is not a simple 3 headed fire salamander that only know how to shoot a slow fireball.
Also, I checked your profile, and I see no D3 profile, so I kinda skeptical about your claim about played d3 for thousands of hours. Just saying.
Define ādeadā because the D3 forum is still active, and the game room got filled up pretty fast in D3 at this moment, and the leaderboard for all classes and challenge rift always got filled up fast and updated pretty often for all regions.
and why do you bring up the D3 state when we are ādiscussingā Hydra? It is almost like you assumed that D3 is dead because they didnāt make hydra works exactly like D2 hydra. 