So true. I thought Thancred's arc was handled very well, especially in ShB. From a heart of gold playboy, he turns into Ryne's father figure and through it manages to overcome his grief over Minfilia and accept her choice and sacrifice.
He should have been the one to defeat Ran'jit and pay the ultimate price. By that sacrifice, he could have been reunited with his true love Minfilia in the aetherial sea.
You have to understand that he was going through a myriad emotions at the time. It's like he saw her as the reason why Minfilia was dead or a constant reminder of that fact. When you're grieving and in denial, you tend to make these kinds of wrong assumptions.
It was especially difficult in his case because, if I remember right, there was the possibility of Minfilia coming back in Ryne's body. But in the end, he made his peace with Minfilia's choice to let Ryne live her life and he chose to encourage her to live for herself as well. It's a big reason why he's like a father to her and Minfilia a mother.
