For me, the relationship with Ziva needs to be developed a fair bit, as it lacks substance. It comes across as though she sees the MC as nothing but a close contact and a means to an end. Compare it to the relationship with Erevi, for instance, and there's no comparison. There's tension, lust and even romance with Erevi (e.g. when she's pregnant and asks him if she really looks "sexy" or when she tells him that he's "never failed her," even though it's hard for her to admit).
It just seems odd that she's been pushed aside to develop the rest of the story arcs, which are obviously all great, but her relationship with the MC seems to really need continuity for it to resonate with the player.