I pretty much said the same thing as you, harrass is good if you do it to lead up to a timing attack but not if you're just gonna herpderp around with mothership archon or even try for carriers.
The reason why this doesn't really work so well vs good players is that you want to have map presence with your army while doing prism harrass, so that you can target multiple places. This means that your army is in incredible danger when infestors are out, it takes one fungal and you're not going anywhere, chain fungal to death. It can work decently if you have a mothership with recall available though.
Honestly I think just about every korean protoss with good PvZ atm are doing 2-3base timings, and I think that is by far the superior way too play. Creator, Rain, Parting would be the top 3 pvz atm and all do timings.
This, immortal sentry all in at the highest level is dominating the zergs PvZ, just look at Blizzard World Championships.
However if you wanna open macro, I 100% recommend opening any form of phoenix build.
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