Currently, the Eloqua connectors sync the tables in sequential order like the below :

1. System Tables

2. Priority First tables

3. Custom Tables

Due to this ordering, a huge delay gets accumulated on daily basis to sync data from source to target. Also performing resync takes more than 2month+ time to complete. This created a huge impact on our downstream consumers. Any improvement to current Eloqua connectors would be of great help. One of the possibilities we could see is, enabling multi-threading for this connector.Please check and let us know if this can be doable from Fivetran end.