I was reading a guide for SMN that suggested having the THM skill Thunder as a cross-class skill for my DOT rotation. However, when I access the Cross-Class skill section of the menu, I only have Surecast and Blizzard available to me as SMN even though I have Thunder on my THM already. Is there a reason for this? And how would I go about getting Thunder on my SMN?

As always, thanks for any and all help