You guys sure are using wierd starts against each other.I think gasless army won't stand long without upgrades (marines without shield are not that good). So if you managed to hold the first push of marines, you can easily win this because of upgrade and tech advantage.
I follow the advice from MerinPally for making oracles if you spot an early attack, if enemy moves out his entire army without static defense on base (and if it's early attack, there is no talk about any kind of static defense) your oracle will kill all his workers and enemy will have to go all-in, surrender, or delay his attack by moving army back to base to defend.
But if enemy decides to go all-in, you need to be sure that you can hold your base with sentries and stalkers (without scan, marines can't see what's going on on ramp and you can just shoot them from above).
Today i lost battle and a game to terran turtle. I've managed to build 3 carriers without getting spotted, killed his third base, and with stalker/carrier/zealot/mothership/immortal army moved on enemy. He had bunch of thors, a lot of vikings and a lot of marines. I A-clicked to his base aaand... FPS dropped to 10 and i couldn't micro immortals to thors and stalkers to vikings. SAD DAY. I think i need to vacuum clean my PC, when it's dusted it acts like this