Huh, shows how long ago I last watched The Clone Wars. I thought Ventress had more relevance in those episodes. I can imagine there is not much else you can do then and I agree that introducing her in this episode makes a lot of sense. It might very well be that her appearance feels less disjointed once I watch more episodes.
And I am definetly looking forward to watching more. I already really liked The Clone Wars in its original form and so I’m confident that once I get to the episodes with a better base plot, everything will click into place once again.