In ZvT when Terran plays bio, what is the best way to snip Medivacs?
I thought that could be Corruptors, but actually they are quite slow and expensive. Hydras are vulnerable to marines.
Surprisingly, Day9 mentioned that Mutas (together with lings and Bannelings) are good vs bio, but I don't understand why: Mutas suffer even more from Marines then Corruptors and hydras.
Could you please advise what are tricks to snip Medivacs? Should I really use Mutas? If yes, then how?
It really depens on the total compostition of the Terran army. (I am a Top 8 Diamond Terran)
My surgestions are the following:
So the hypothesis should be that the more bio the Terran has, the more infestor heavy your army should be. By saying this, I would recommend that you use the unit you are most confident with. (infestor or muta)
The trend on the ladder for the Zerg facing MMM, is Zerglings, Banelings and Mutalisks.
Mutalisks are great for sniping Medivacs.
I'm going to explain why Day[9] said that this is a good counter:
Surprisingly, Day9 mentioned that Mutas (together with lings and banelings) are good vs bio... but i don't understand why: mutas suffer even more from marines then Corruptors and hydras...
The reason is all based upon how your army engages their army. If you have zerglings and banelings rolling into a bio ball and they do not split, their bio ball will be massacred by the baneling splash. But if they do split, their medivacs are sitting targets while the ground army tries to avoid the banelings. If they do move back/run away/kite, usually using stim, their medivacs are vulnerable to attack because they move slower than the stimmed army.
The best way to accomplish these types of engagements is to have your zerglings and banelings on one control key and your mutalisks on another. That way you can control when each force engages. You can even try baiting their bio ball into stimming and chasing your mutalisks with your zerglings and banelings out of their sight. Then when they're chasing your mutalisks you surprise them with the zerglings and banelings forcing their ground army to either take heavy losses or retreating.
To answer your question about how best to snipe medivacs, the easiest answer is to simply target fire. If you send your entire army (mutalisks, zerglings, and banelings) in, the AI will simply go by the default action, attack what is attacking me. In that case they won't target the medivacs until all the attacking units of the bio ball are dead. Again this is why having the two forces on separate control groups is important. You can let the zerglings and banelings attack as they please while you have mutalisks target fire medivacs and have their glaive bounce still do additional damage to other units/medivacs. Mixing in a few corruptors with your mutalisks will also help the cause, but not too many of them as they will become dead weight unless you are planning to transition into brood lords.
It's difficult to direct a response against the question, because it depends on a number of factors including your build, the time (e.g. midgame/lategame), etc.
However I can comment on the muta/ling/bane strategy you mentioned. In those types of builds Zerg players drive back medivacs with a combination of spores, speed zerglings, banelings and mutas. Ideally a combination of those units are used instead of a single unit e.g. only lings. The reason for this is because a good drop is usually placed in a mineral line or a corner giving very little surface area making lings very cost inefficient. However a combination of lings + banes is effective because they can't kite, meaning they can only lift, and that's where the mutas come to punish the lift.
Though mutas are cost inefficient vs marines, a good clump of mutas can still handle a small group of marines. Often it is better to lose a few mutas vs losing a base, again I'm giving very general advise. Another advantage that mutas have against medivacs is that they're fast, as such they are good at intercepting drops before they occur or as they are leaving your base.
Lastly the greatest defense against drops in my opinion is scouting. Properly positioned overlords and good creep spread will tell you a drop is coming giving you ample time to position your units to either counter attack or defend.
Against this is more of an advice rather than answer, but this is way too long for a comment :P
Corruptors and Mutalisks can be used to snipe Medivacs, but it can be expensive as you say, and unless the marines are occupied with Zerglings or Roaches or something, the air units may be torn to shreds.
A better strategy with Mutalisks in my opinion is to abuse their speed and mobility. Mutas can hit one base, then when a bio army gets there, quickly move to another. The only way Marines can catch you is with stim, but by using terrain you can kite them around, forcing them to re-stim and use up Medivac energy healing.
The Terran counter to this is Vikings or Thors, but Thors are even slower, and Vikings can be taken out if you catch them out of position. If your Mutas/Corruptors/Hydras can team up and hit them when they don't have ground support, they will go down quickly.
Day[9] is right (as always). A marine hit by a baneling can not be healed so a pro needs to scatter his marines. Lings run faster and get lots of free hits while marines are busy splitting and running. The terran deathball is now more like a fluffy ball so you can sent in muta's, you could snipe medivacs or just support your troops. If your opponent has siege thanks you should snipe those first since they grind your ground forces. You could also use your muta's to kill of reinforcements or the rest of his army if you get them to retreat.
Investors are extremely effective against bio too, in combination with a couple of banelings they can be extremely efficient cleaning up a bio army.
