I disagree.

I am an officer in a casual raiding guild. Our current raid leaders (we have 3 so we don't fall apart if only one can come to the raid) were all recruited straight out of hardcore guilds - albeit not straight into a Raid Leader position.

Yes the progress is slower, but I think our Raid Leaders gain something else from being in our guild - a more friendly forgiving environment, less demanding raid times and a ton of appreciation and respect from our members.

I would recommend keeping an eye out for "1. [General] LF casual raiding guild" and talk to those people. Ask them about what kind of guild they're looking for and what kind of raiding they've been doing. In 5 minutes you'll know if they're worth having on your team and be upfront about your guild and your progression. Be honest!

Then promote from within when they have gained some respect/visibility in the guild. If they have what it takes to lead, it'll be apparent from the first raid/vent experience.

Good luck. There are great players out there.