I played 2 of 3 games, the latter ones. Whatever Tali was in the first game is not the person she was the majority of the journey. At the very least she should had realized her incompetence and message Shepard "hey Shepard the Quarians are planning a secret wars with the Geth while reapers are attacking, I know how you bail me out last time, can you tell me what should I do?"
Edit: I'm planning on buying some DLC, which one is better. Omega or leviathan?
Leviathan is way better than Omega. You explore more planets and there is more than only combat to do. You also learn more about the Reapers, while Omega is just about retaking Omega...which might be more or less interesting to you depending on how much you liked Omega and Aria in ME2.