So I went and looked at your highest parse.
First, you’re never going to parse well in a raid that is 5 healing with 21 players. Healing is finite - you only need to heal so much damage. The more healers there are, the more you’ll get sniped. Your shamans, as an example, are all between 60 and 70% overhealing. I seriously have no idea what there even is for you to heal when stats like that exist in your raid.
That said, you’re doing a couple things here that are hurting you. From most to least severe:
You’re not casting your major spells/not casting often enough in general
Through the fight, you could have cast Prayer of Mending 25 times, but you casted it 5. This is your absolute most important spell if you’re playing Oracle Priest. If it helps, you can get a weakaura or addon to track the cooldown of it and make sure you’re always hitting it. People do not need to be hurt - you can just toss it on the tank. PoM’s best feature is it heals when that player takes damage, so it’s always ahead. You want the stacks out there even before the damage is happening.
You casted Renew 6 times out of a potential 21 casts. Renew reduces Sanc’s cooldown by 8 seconds, so that’s a loss of 120 seconds - so you could have had another 2 sanctify casts. Though realistically during Apotheosis Renew would be 24 seconds off, so you could have had significantly more.
You could have potentially used Apotheosis 3 times (though realistically you’d only get 2 good uses) but you never casted it. Alongside that you’ve casted only 8 serenity casts and 5 sanctifys. You actually did good considering you didn’t get a ton of CDR on them - but you should have been casting other spells to bring their CDs down more which would have allowed way more casts. Also, you only hit Prayer of Healing once despite taking that talent.
Your shamans are beating you here because they’re casting into people at like 90% health and just sucking up that healing - and you’re never even attempting to heal players that high with anything but flash heal (which is going to be too slow).
You spent a good 61% of the fight not healing at all, and 43% of the fight simply casting nothing (even damage). Always be casting is a general rule to learn. Even if you feel you can’t heal, you can Smite and that might get you some surge of light procs for free flash heals. 
Your Talent Build
I’m very much a ‘play what you want’ kind of player when it comes to talent builds, but your current setup doesn’t even make sense for that, really. You don’t have the max amount of points in the final tier of talents. You have a point in Prayer of Healing (and Prayer Circle) even though you’re never casting the spell. You have a point in Desperate times, but nobody in the raid is dropping below 50% for you to make use of it, etc.
You’re also only taking one capstone talent in Divine Image, but you’ve got pretty low uptime due to low holy word and apotheosis usage.
For reference, here, in raid our most powerful talent synergy is Eternal Sanctity (under apotheosis) and Answered Prayers (bottom right). You want to be getting free apotheosis procs and blasting out holy words during it. Especially if you’re playing Oracle, who gets extra PoM stacks. You should be thinking of your Holy Words as your first option in raid, rather than as emergency heals. Don’t wait for people to get low to use them. Just use them so that you can start building them back with your other casts.
For a build that’s close to yours and still Oracle, I would recommend swapping to: https://www.wowhead.com/talent-calc/priest/holy/oracle/DAQAEBVBUQRRREoVGkUDAFAPVRAVBVFVVFUCEFQCVAEFVVUCBA
With this build, your main goals are cast PoM off CD, cast Renew off CD, Cast Holy Words (even in light damage), and ESPECIALLY cast holy words when in Apotheosis. You also have Chastise in this build - which is good because of Divine Image. Make sure you use it to proc your naaru if you don’t have any other holy words.