I thought the requirement had been level 48 for SL zones. That didn't stop me from using a scroll when the guild was called to rally in the Dendrome. I figured I'd get some error message right away, but that didn't happen. Here comes 95% loading screen... Shirley there will be a redirect here... nope.

So there I am in Dendrome at level 46 fighting a zone boss. Get the achieve, everyone runs off and I suppose I should've asked for a Cape Jule guild banner, but decided to hoof it. Died a couple of times, got a few portals along the way and a Torvan Hunt achieve (already in progress). How low a level do guild rally banners work for SL zones? No story nor carnage quests were available, even at the starting portals until level 48. Though some of the Ashora dailies were available, which might be a power leveling option...