Just to confirm, you both killed the Bosses in the NEW world not a previous one yes?

If so might be a bug. If you meant Killed all the bosses prior to setting a new Mistlands fresh world then No you wont get raids or if you do it'll be the lowest level ones only.

Bosses killed in the actual world is what the gate is for raids. A toon can be the slayer of them all but go to a new land and never get bothered hardly at all if nobody their had done any boss killing.