You are healing with a very strong Resto Druid which from your logs they are mopping up a lot of the group healing which is the Shammy strength. If your raid is making the kills then healing is good. The boss kill determines if the healing was good. If your team is keeping the raid nice and steady without those “oh s#@&” moments then all good.
To improve on the logs then cast more Chain Heal. It seems very low in all your fights. I know a lot a Shaman don’t like Chain Heal spam but there is a reason so many use it and why this forum is named “Chain Heal”. In my case it’s my top heal by a fair margin. I pumped 900k HPS on Demonic Inquisition with some quality Chain Heal spam. Here is the log https://www.warcraftlogs.com/reports/2mbjVnBfwPCQqT36#fight=1&type=healing