Question on Assassinate

[Geonis]

Per DDOWiki:

Assassinate
Usage: Active
Cost: 0 action points
Performs a melee attack that on a successful sneak attack can kill a living target instantly if the target fails a Fortitude save (DC 10 + Rogue Level + Int Modifier). Even on a successful save, the target takes 10d6 additional damage from the sneak attack. Can only be used while stealthed.

While rednameds would be immune to the insta-kill portion, are they immune to the extra damage?

[Hawksen]

Red names take the damage.

[Draccus]

Can anyone confirm that the extra damage is actually working? In a hundred bazillion million assassinate attempts, I don't ever recall seeing a sneak attack on a save any bigger than my normal sneak attack. With the extra 10d6, my sneak attack number should be an average of 35 hp higher than my normal sneak attack. I would DEFINITELY notice that and would think I'd see sneaks in the combat window in the 140s Instead of the low 100s.