Thank you for your feedback!
This feature has high development cost, so I’ve changed basic builders power from 0.0 to 0.1 for now (wooden workers have 1.0 power). I think this is fair change for a while, since it will also smooth player experience before wooden builders are unlocked.
Also I usually build 2-4 builders and then upgrade them one by one. This way I always have at least 1 instance of builders to automate process.