It sounds like you're building a large army and using it to gain map control, but then are falling prey to things like drops and backdooring.
If you have map control your first thought should never be: Crush my opponent, as you're essentially sacrificing an advantage (map control) for an unsure victory (because he doesn't control the map doesn't mean he can't take you). Instead your thought should be: take the map. I think you'll find this change in philosophy will lead to situations where you have a much more powerful economy than him and you're able to kill him with attrition.
Now if you're falling prey to things like BD here is a quick check list for you:
- Are you scouting? an Observer should be the first thing you build out of Robo. If you don't go Robo, a Hallucination works just as well. Sometimes scouting means sacrificing some Zealots in a pointless charge to just get inside his base.
- If you're scouting, are you seeing it coming? Overlords on the edge of your base, Starport with Reactor + 3 Rax, all of these are indicative of certain strategies you should watch out for.
- If you see it coming, how are you responding? If you have map control that means you should be able to respond quickly. Shutting down these back door attempts is often a bigger victory than a straight up conflict
- Finally, Do you have map control? If you don't have map control that means he does, and if he's beating you with map control then your problem is not "how do I deal with a base trade?" but rather, how do I regain the advantage.
Since the last question was more about Void Rays I concentrated on more diverse Protoss Anti-Air
Gateway
Since Protoss strategies usually revolve around heavy gateway units, Stalkers are more or less a must in anti air confrontations. The most important rule of Stalkers is: unless you are chasing, never blink into battle. This is key, because as a tool, blink is far more effective as running away or chasing than it is as an opener. Stalkers are a very fast unit, so the only time you should ever feel the need to blink into an enemy is when they're running away.
Blinking away has two important aspects to it:
- Mass Retreat
- Moving the Front line back
While retreating is often times a necessary thing, it's the latter, that makes blink such an effective tool. When you find yourself against engaged in a battle, you'll usually notice that your vanguard (front units) take the brunt of the damage. If you blink them away as they take damage, the damage will spread more evenly over your whole force and your Stalkers will continue to do damage from longer periods of time.
Protoss Air
If your build is designed around Air units there are two important things to remember:
- Phoenix can shoot while they move
- Void Rays can shoot while they move
Most people don't know the second one. The key to any Protoss air confrontation is to make it a mobile one. This is why the speed upgrade for Void Rays is so crucial. Now Phoenix and Void Ray have different use cases, Phoenix are effective against light, and Void Rays against armored. Based on what your opponent is going you have to adapt. If you're seeing Muta heavy, go Phoenix. If you're seeing Viking/Corruptor go VR. In a PvP its usually whoever has better macro or more upgrades who triumph... you know, unless you get High Templar
High Templar
Usually built out of an early 4 gate strategy, HT are one of the most powerful units in the game. Psionic Storm needs no introduction, but don't forget about Feedback. Feedback has the unit property of being amazing against unexpected units. Allow me to list a few:
- Ghosts (no surprise)
- Infestors (no surprise)
- Dropships (wait what? healing uses energy?)
- Phoenix (how do you think they lift)
- Ravens (as well as point defense drones)
- Battle Cruisers (Oh yeah!)
- Corruptors
- Even Mothership
I have definitely had games where I won with just HT/Zealot just because of how versatile this unit it. What's more they can easily be transformed into damage soaks (Archons) to break Siege Tank of Void Ray lines.
Having trouble against Mass Void Ray? Strangely enough Psionic Storm is surprisingly effective against Void Rays. Because of the charging nature of their attack, many players won't immediately move their Void Ray out of danger.
Conclusion
As always, the key to beating a PvP army often lies in doing something unexpected while your opponent is doing the expected. Use Observers to try and retain the advantage in the game of information warfare.
Best Answer
Are the Protoss fairly micro heavy in the early game?
I agree with other posters that Protoss benefit from micro, but that so do all the races. Protoss do get an early "caster" unit in the Sentry, and do benefit from micro to save wounded units since their shields recharge, but then zerglings benefit from careful surrounds and marines benefit from grouping and stutter-stepping.
It's true that you see pro players using forcefields to incredible effect, but you'll also see them do amazing things with reaper scouting/harass, expand-blocking with workers, and so on. Use these tactics if you can, but they're by no means required unless you're in the top levels. At my level I rarely see sentries, let alone good forcefield usage.
Can an underpowered computer limit your ability to micro in a game?
Sure, but if your PC is lagging enough to mess up your micro in the first battle of 10 vs 10 units, it will be completely unplayable in the later stages of the game. Therefore if the game is still playable in the late phases when you have big armies, you should have no problems early on. Later-game micro could be a problem, when you have tons of units, but that varies PC to PC and you just have to try it out.