FWIW, I do agree with everything you've said about Seaver here. It makes perfect sense to me. I think what I like about her is actually the actress, who seems really awesome, so it's helped the character to grow on me. But you're not wrong at all. She IS just there, I agree. She could have been written into the show a hundred times better. I don't see why she couldn't have been a full fledged agent when she entered at least.

Also, fantastic point about Prentiss. It's probably due to the fact that most of the writers now are new and it seems like they haven't watched any of the older episodes, so they have no clue.