right away I noticed those stalkers have way to little dps to trade well against the Hellbats considering the fact there so great tanking units.(even though there should have been a little bit more micro on onetrickponies side.) also immortals don't get there extra damage versus Hellbats and the collosi got beat by a good amount of Vikings well what could he have done? Obviously sky toss would have faired very well with the army comp demuslim had but what if your only in a position where a ground army can be made what then?
Lets take a look at the hellbat it is a good damaging unit that tanks damage and can be massed, it's weaknesses it clumps and it is fairly slow with a low range. So I propose this set up could really do well against Hellbats an undetermanted amount of siege tanks and Vikings. You would want high Templars, sentries and two robotics facilities. I figure the aoe of the HT plus good Forcefields and immortals plus a few stalkers (ugh) to help tank damage would be able to effectively deal with the opposing composition because it is slower. There's also bonuses hallucination to keep tabs on the enemy there composition base structure ect Feedback for the medivacs would really help prevent drops. Easy switch to dropships for zealot pressure (HT?) and could quick change to collosi if the try switching to marines and faze out Vikings.
All though of course there's draw backs HIGH gas cost Although that composition is rather slow attacking with high damage so you could do one forge on attack to help alleviate some cost since armour and shields won't be affected as much plus guardin shield could be used. This comp won't be nearly as affective versus marines so you need to scout the tech switch. They high gas cos is why I chose immortals instead of collosi from robo 250mins 100gas versus 300min 200gas per unit for more mineral spending also dropship with zealot pressure as another mineral dump. Can someone test it out? Unfortunately I don't have the apm to put this build through rigorous testing any feedback would be really insightful.