How much percentage wise is considered within the error. For example, I tried BiB with my resto druid and I got the following simulation with nothing locked: https://www.askmrrobot.com/wow/simulator/report/0343a3ae25ce43929fe42a44bd5f1601
When I locked the azerites and the trinkets I wanted (and re-optimized) I got the following sim: https://www.askmrrobot.com/wow/simulator/report/6c9e8bb59aad4322ab08ee0362700524
As you can see the second sim is around 600HPS better. If 600HPS is not negligible then I think there is something weird with resto druid BiB.
On the sims I put +6 modifier. Also, my export is: https://pastebin.com/xNkxscxz