EPTRight now, the extensive one base, slower expand play T's have been doing is really a reflection of how long it takes for the other races to get to efficient counters to bio.
To really deal with bio, the other races really need to be on two base and have enough gas to unlock critical techs. After the tech is unlocked, the tables turn and P/Z can mineral dump + gas dump much more efficiently than bio T. In both matchups, MMM (marauder especially) become an inefficient use of minerals/gas compared to ling/baneling and zeal/storm.
I think people are very close to understanding how to safely FE against T bio/1or2base plays, and soon T is really going to have to adjust how they play compositions in longer games. T always risks running out of steam trying to shoehorn aggressive bio play against macro players. Instead this writeup focuses on how to decouple min/gas for T to match other races' efficiency.
I personally favor macro games and push almost every game into 3-4 base; I don't imagine that the game is designed to be won at 1-2 base (with T being at disadvantage after) - game like that will be figured out too quickly, and devolve into RPS with BOs. So this discussion is really with the intent of seeing what T composition should look like off of 3+ base.
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Note:
Income per base (~800 min/m, ~250 gas/m)
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TvZ
Once Z makes it to late tier 2, and unlocks all his techs (including speeddrop), bio is no longer viable. Off of a typical reactor FE, you will have something like 1raxTL, 2raxR, 1 facTL, 1 portTL. This is basically what 1.5 base gives you. Let's take a look at what saturating the second base and transitioning to the third base will look like (say we gain another 1k min/m and 500 gas/m).
Basically the only unit that is viable as a mineral dump is the marine because Z can always dump all of his gas immediately into mutas. Marine also happens to be generally decent against everything (lings, roach), and forces the Z to trade gas for minerals through banelings.
You need to match 1 medivac / 8 marines to cover stim costs, and therefore eventually be adding a portR. With the remaining 400 gas or so, you can afford approximately 2 major gas dumps / minute. You already have portTL from earlier, so that's basically adding another factTL. If you are against hydra/roach, then you can just dump the 400-500 into tanks, and plow his ground.
Against ling/baneling/infestor/muta, tanks are really not that great. Combat basically changes into how many marines can Z get with his banelings, and how you can support the remaining marines through what is left. My thoughts include
*You can afford 1 raven / minute + 1 thor/ minute. Raven in crit mass will provide stability against baneling + muta. After being bombed, you can recover the ground by dropping mass turrets; this is really the ideal unit against Z T2. Thor are nice too because they provide a damage sink that roach provide for the Z. You need to last as long as the Z in combat.
*Since the other factTL is not occupied, you can just crank hellions to aoe the lings (marines clean up).
*You can cut one gas unit you don't need to fit in a ghost every once in a while. You will want to EMP the infestors.
*Going late, you will skew more raven if you sense more T2 or air play (BL + corruptor) and not so many ultras. VS faster ultras, if you miss your attack timing, probably skip the raven and just mass up thors from both factTL.
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TvP
This matchup is really different because if you don't bio, you really can't attack in any reasonable amount of time. P units have too much hp, and require you to really have critical mass to engage on him. It takes 13-14 vikings to one shot a colossus, and 10 tanks to clear out immortal shields.
But, zeal + storm + colo completely deny any 3 base bio play. In fact, P can safely FE with 1gatenex pretty reliably on almost every map. Any allin off one base, can be blocked by some combination of pulling probes + FF, or in the case of banshee allins, cannons.
With bio, there comes a point eventually where P has critical mass colo + storm and just cleans up your army before you can volley. The issue is that zeals also are too cost efficient of a sink against marauder, and P has used his gas much more efficiently than you (medics are not great at killing things).
Here is an example of how poorly bio scales (at one point P has 2k in bank, and is down 50 food, but trivially claws back): http://sc2.replays.net/replay/Sc2Replay.aspx?ReplayID=2200
What's wrong with 111? It's just very slow and defensive. Banshee and tank are both not that strong for pushing out to your natural - P has any number of options to slow you down and make sure he takes his expo, and third faster than you. The fundamental issue is that those early T gas dumps are really vulnerable. If you want to take your expo, and your third at any reasonable pace, you really need to abuse the window before P can reasonably take on your bio army.
But, 1 rax FE (-> 2rax reactorport vs 1 base, or 2 rax banshee sneak vs FE) is not safe on most maps, and requires a PF on the maps it does work on (or will be unable to hold VR 3gate).
Instead, what I've been doing is 1rax FE IN BASE. You get fast reactor on the first rax while adding the second raxTL, and factory. Without factory, you will not be able to deal with VR or colossus openings. The one piece of scouting that you can get reliably (I generally burn a scan when both OC are up) is when/if P expands. If P expands, you can float earlier, and possibly aim for proxy banshee. If P plays one base, you will be blind basically to what he is doing. You need a round of vikings from the port asap. You will be able to push out with stim + medivacs + vikings against any P composition at around 60-70, and land your expansion (should be no later than his) (compare to 111 where depending on build you can be delayed greatly).
I like to add on 2 more raxTL. And take 3rd ASAP, attack and pressure him before charge/colo mass. But at this point the window for bio is closing. With your third up, you will need to finally utilize that factory.
Off each base, you can support 2 hellions, 1 tank, 1 viking. With 3 base, your production looks like 4raxTL, 1-2factR, 2factTL, 1-2portR. You will be able to split production 1/1 marauder/hellion, and gas dump into tank/viking.
There are two critical masses that are important here. You will want to have 8-10 hellion every fight to burn down as many zeals as possible in 1 shot. The other critical mass is 14 vikings to one shot colo. Depending on P production, you should sync your attacks with these numbers.
If you pure hellion, they will get shredded too quickly by mass colo, and you really do need marauder to soak hits from everything. If you just pure bio, then zeal + storm will just deny any sort of advance.
What combat looks like is that you will now be able to trade armies efficiently against P, hellions completely nullify zeal mineral dump. The faster you can clear out zeals, the more time your marauders will have to hitting the stalkers. Tanks need to be targeted on stalkers manually - splash damage will destroy your army if you let them target stray zeals. Whenever you have a comfortable amount of vikings, you can dump gas into dropships instead, but vikings are #1 priority to keep at crit.
Ghost/Raven are small minor boosts to winning fights. With critical tank mass sieged, P won't be able to approach without losing all his shields, so EMP is not amazing. But, a good P will force you to run around and get the jump on you, so EMP is excellent in this capacity - mimicking the initial burst of tanks that you will miss. Raven as well offer you protection against getting jumped.
So the two incredibly efficient min/gas dumps are that P has are under control - zeal by hellion, and mimicking storm with tanks.
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Some comments about FE vs P:
Against P, I had been doing 1rax FE into bio, but this is really only safe on maps where the natural blocks the main (LT, steppes). Bunker + barrack spam works only against straight up 4 gate play, but you need a more robust FE against the two dangerous one base plays - 1gateVR->3gate (charged VR on rocks/pylon), and 3 gate blink.
To deal with this, you really have to assume you no capacity to scout reliably, other than to see if P has not taken an expo (therefore doing 1base). So my build looked something like 1marine raxTL, 22CC+bunker with 1 marauder (hold aggression on low ground), reaper scout to count gates, swap rax to make reactor and second rax at TL, ebay at 1/2CC, PF when done.
Then you add either more rax or fact + gas, depending what your reaper sees. Against late gates, I would tend to get faster port and a turret at the PF. You will need turret + viking to hold the 2 VR push.
Against the drop/blink plays, you will need marauder marine in your base to chase down the units.
Without PF any FE gets busted simply by 3gateVR. PF allows you to safely cut bunkers and additional rax to speed to viking. It also allows you to leave your expo undermanned to chase units in your base. But since this build isn't really safe on most maps, I've started playing around with just expoing in base (since you won't be saturated anyways) and relying on the choke to hold against 1 base play.
