As the title says, the generic Slann have been very lackluster, to the point that nobody picks them. It's much better to get a Saurus (and now Skink) lord and a Skink spellcaster, as both will end up getting mounts.
I love the Slann though, and how in the lore they are the most powerful spellcasters by far!
CA, I know we don't know the changes yet, but I hope you will consider the generic Slann and give him some love as well. After all, it costs a full rite to get them in the campaign. So I would love it if they could be the most powerful spellcasters by far, in exchange for not having a mount.