First let me say that this is more of a response to rushes generally, which have an extremely high win rate.
This post will be about Bunkers in comparison to other defensive structures based off of resource cost. We will look at build time, DPS, hit points, utility, range, support options, and upgrades
First we need to establish the cost. 1 Bunker (100) with 4 Marines (200) costs 300 minerals. This is 2 photon Cannons, or 2 Spine Crawlers.
To start let’s look at build times. Bunkers build in 29 seconds as do Photon Cannons, but Spine Crawlers build in 36 seconds. The difference here is the Bunker needs Marines which take 18 seconds to build 1 at a time which is 72 seconds. Even if you build a Reactor it takes 36 seconds to build which means it takes 72 seconds to build 4 marines 2 at a time. The best case senario is having a Barracks with a reactor already on it which would put you at 36 seconds. This means in best case scenarios you would be slightly worse off then a Zerg player which could build 2 Spine Crawlers, which net you more DPS.
Next let’s look at the DPS difference between the structures. A bunker with 4 Marines does 39.3 DPS, two photon cannons have a DPS of 44.8, finally Spine Crawlers have a DPS of 37.8 increasing to 45.4 versus Armored targets. Keep in mind they have have the Least hit points (HP).
HP is next, we are going to be looking at effective HP, that is how much damage it actually takes to kill the building and units inside including armor, this is simpler then it sounds. Bunkers have 400 HP with 1 armor and 4 Marines with 180 HP with 0 armor. Two Spine Crawlers have 600 HP with 2 Armor. Two Photon Cannons have 600 HP total, 300 Shields and 300 HP, at Armor 1. From here we can see Zerg have the most durable defence structures, prior to support and upgrades. Protoss have slightly more HP with more overall armor. Which means Terrans have less HP. An example would be against a single Marine the Spine Crawlers would have an EHP of 900 while the Bunker and Marines would have an EHP of 660, and the Photon Cannons would have 720 EHP. This of course varies by unit, but regardless of the situation the Bunker and Marines will die faster no matter what.
Utility can be as, and sometimes more, important then Damage and HP. Photon Cannons can attack both ground and air and have detection. In short no matter what is happening Photon Cannons will help. Spine Crawlers can move, which allows them to be built in a safe location, then moved to where you need them. Bunkers with Marines can shoot air and ground, and can move, but become hyper vulnerable while on the move. The Bunker also has the salvage ability which let’s you recover 75% of its cost. Over all Bunkers have some utility but tead to fall just short
The ranges are pretty strait forward. Spine Crawlers have 7, Photon Cannons have 7, Bunkers add 1 to the Marines range of 5 putting them at 6 range.
Support options are a bit more wonky. Protoss have probably the widest range of support. With the Shield Batteries allowing an increase in shield health by 300. Sentries allow for temporary walloffs for free and with enough of then a permanent walloff, every unit you build has 1 armor which makes then moderately durable, and to top it all of shields regen very quickly which means if you do not apply constant pressure you allow Protoss stronger. Zerg have Queens which can Infuse and are just generally good at defense, they are also a safe investment because you use them for creep spread. Terrans are again in a very strange place, they can heal much more but it costs actual resources and mining time. This puts them at an even higher cost then they already were. They really have no support past that without heavy investment.
Up to this point Bunkers cost more for, longer build times, less or comparable DPS, less hit points, less utility, less range, less support options which cost more. Now we get to upgrades, which is pretty strait forward. Photon Cannons have 3 upgrades and Spine Crawlers have none. Bunkers have DEEP BREATH Neo-Steel, Infantry Weapons 1, Infantry Weapons 2, Infantry Weapons 3, Infantry Armor 1, Infantry Armor 2, Infantry Armor 3, Stim, Combat Shields, Concussive Shells, and thats it I think. Here is the biggest strength of the Bunker. It scales amazingly well going from 39.3 DPS to 215.2 DPS.
So what is the issue? The issue is to get that sweet damage, the increased health, the longer range takes a LOT of time, too much time in fact.
The argument is simple. Because Protoss have better support options and quick HP Recovery when not under pressure they survive rushes more often, and as a result they survive longer in tournaments. Zerg are better off due to having upgrades built in to the defensive structures and the support units which translate to mid and late game well. Terrans, however are in a bad place they have to spend a large amount of resources to have a defence 600 minerals for 2 bunkers and 8 Marines to kill 2 zerglings a second. Which is not very good value. That isn’t including repair costs which are minimal, and lost mining time which is not minimal 102 minerals per SCV per minute. 6 SCVs repairing for 30 seconds is a mineral loss of 306 minerals. On top on that you end up with 8 Marines which means if you don’t go Bio, your units are also a bit of a waste. So if you piviot into Bio your opponet will be ready, if you piviot into mech then your going to be between 5-10 units behind.
The question is how do we fix this problem? You can’t boost bunkers because it will be used in bunker rushes. Adding a cheap unit will again be used in rushes.
The only thing I can think to do would be to add a cheap barracks add-on which is a turret. Even that would probably end up turning Rax Rushes into even more BS.
