Oh please.
Nathema can hardly even be considered a Sith ritual. Tenebrae grabbed a world-consuming superweapon entity, turned it on, then allowed it to destroy all life on Nathema (including 8,000 Sith Lords) as it powered himself - which it has the ability to do.
It's frankly a less impressive ritual than Revan's Temple of Sacrifice ritual, since at least Revan had to do most of the work himself rather than turn on a hyper-intelligent robot designed to consume worlds.
Worse yet, Revan apparently knows rituals that can planet-wipe without need of any technology nor followers, as indicated by the Forgotten Terrace fight. As for the thought bomb, Revan somehow studied the effects of a superweapon and then made a miniature, Force-user powered version of it that yielded the greatest Force nexus ever (more so than Nathema).
As for Bane, there is no indication he considered Nathema more potent than the thought bomb. He probably scratched his head because one of the required items to conduct the ritual was "potentially galactic-destroying supreme AI intelligence superweapon."
I have no clue why you took this as an insult on Vitiate either - you should want him needing a superweapon to do this. It shows his immeasurable growth from needing a literal deity to cleanse a world to being able to do it himself while weakened on Ziost.