Starcraft – How to keep sentries and templars in the center of death balll

I've beat Terran with Protoss using photon rush.

1. Build probes constantly, 1st build probe will go to opponent, all others - go to minerals; 10-12 actually should be enough.
2. Build the 1st pylon outside of the opponent's start location - if you build it in the opponent base (after the choke) he will attack the pylon with large amount of SCVs. The Pylon should be built as close to the opponent base as possible.
3. Build 1 forge.
4. Build 2 cannons close to the opponent base - they will shoot up the ramp soon.
5. When these cannons are almost complete, send a probe to the opponent's base and build 1 cannon (you 1st pylon should give enough space for 1-2 cannons).
6. Opponent will try to attack your building cannon, but your first 2 cannons should be able to protect them. Keep you probe from being killed by SCVs/marines.
7. Build new pylon close to new cannon, once the new pylon is done, build 1-2 additional cannons not to far away from the 3rd cannon; it should be able to protect the new building. The new cannons should also be able to attack the command center.

After the last cannons been build they will start shooting the command center. The AI will give up quickly.

I did the above and finished sometime around 4:30.

First off, you should be getting Stim before Concussive, I'll explain why in a second.

The Marauder is both a vastly overrated and underrated unit. It has pitiful dps (against anything that isn't armored) and largely exists as a meat shield for the much higher dps, much lower hp, Marines. The ideal Marine/Marauder ball is relying on Marauders to tank while Marines dish the damage. Let's take a closer look at the Marauder:

125 HP
1 Armor
10+10 damage (or 6.67+6.67 dps)

Against your average Zealot that 1 armor is going to cost him ~15% of his damage, while the much more cost effective Marines dps him down. Additionally, any Stalkers only do 70% as much dps (as the Marauder).

So Marine/Marauder is already set up nicely against Zealot/Stalker, which brings me to Stim. Marines, being your real dps here, really need Stim to help take out the slower Protoss units and it also gives them the ability to kite. Compared to that Concussive Shell is just icing. In fact, you'll see a lot of Terran (like Jinro) move out just as Stim finishes and Concussive starts, because they want to maximize the timing window Stim represents (and because Concussive's shorter build time often means it'll finish just as they start engaging).

Now you asked about earlier pushes than Stim, and the list is very short:

• Marine Rush
• Bunker Rush

Both of these plays fail against a 1 basing Protoss player. The truth is, Stim is very early, and very powerful, you're not going to find anything better before it. If you're consistently losing a Marauder heavy ball while dealing early pressure, then I suggest you reexamine your composition. Most 3 Rax play has an even amount of Marauders and Marines. Earlier pushes (like 2 Rax), tend to be very Marine heavy, with a few Marauders thrown in to act as meat shields.

I hope this helps