Salesforce developer support had to enable the 'Bulk API' feature on our org.
Once that was accomplished, I created a permission set and in the 'System Permissions' area I was able to find the check box for 'Bulk API' then I assigned myself to the permission set.
Thanks Salesforce.
Only marking fields as external ids as you pointed out is the only way an end user can have a field indexed. Other fields such as lookups (and master detail relationships) are indexed automatically.
For what you are requesting there's really only 2 options. Create a snapshot like sobject / table to have less records you'll need to filter through for reporting. If that is not possible, requesting fields to be indexed would be the other solution.
Before requesting fields to be indexed, you should take a look at your report and confirm there are no other filters which are currently indexed narrow down your list of records being pulled back. Some suggestions are using recordType, using default picklist which salesforce has indexed such as Stage/StageName, using CreatedDate/LastModifiedDate, and using other lookups fields as those are indexed as well. The last thing you'll want to add to your filter are fields that are not indexed.
I also suggest when creating a case with Salesforce, is to make your request as simple as possible. I know it feels good to get some struggle and emotion off your chest when creating a case, but I've had the most success when just writing a case with the bare minimum and being detailed as well. For your case I would write something along these lines:
I want to request having some fields on the sobject "Account" to be indexed. The fields below are the ones I am requesting:
Webinar_UTP_First_Attd__c (DATE)
Webinar_UTP_Latest_Attd__c (DATE)
Webinar_UOC_First_Attd__pc (DATE)
Webinar_UOC_Latest_Attd__pc (DATE)
Reason for this request is due to report timeouts which occur very frequent. If you have any questions, please feel free to reach me at PHONENUMBER
Lastly, as I've had issues in the past reach out to your AE, they are in charge of keeping you happy so Salesforce can keep their clients. See my own post here with my struggles with salesforce support.
Best Answer
There's a few things this could be: