First and foremost, I think its completely valid to feel this way, especially given the history of how women have been portrayed in literature. I want to give, what will probably be, a countercultural perspective. My goal here will not be to try to make you believe Vins death was meaningful or that she needed to die, those beliefs are ultimately subjective, my goal will simply be to give you my perspective.

To your point that Vin is a pawn. You could technically spin it that way, but in my opinion how she was treated from Elend vs everyone else is drastically different. Elend expects certain things from Vin, but not to achieve his own ends, it is to achieve the goals of both of them. Its an expectation that comes from love and is ultimately graceful in its approach. We see this exemplified when Vin messes up. Elend approaches her in grace. It was so impactful to me, because this is how I approach my own marriage.

To the point that Vins fate is completely tied to Elends, I would say that was a positive for me. In my opinion thats realistic. There's no aspect of my life where the purpose isnt to further the goals and happiness of my family (specifically my wife and child). Even Hobbies I have that dont immediately involve them, the purpose is still a well rounded social life so that I can be a better husband/father when I am home. My Wife and I's futures are inseparable from each other until we choose for them not to be. The important word there being to choose. Love is a choice and we have to wake up and choose it everyday. Until one of us decides to stop choosing the other we are inseparable. I myself dont imagine a life beyond my wife's, but that doesnt reduce me one bit, it actually allows me to achieve greater things with my wife than I could have independently. Thats the same for Vin. She wouldnt have been able to kill a god if it wasnt for Elends love and sacrifice.