Thinking about it, i guess Uther becoming a forsworn makes sense. Especially if we assume Arthas will come back, Uther is doubting his worthiness as a Kyrian because of what happened to Arthas, and whether his actions were the cause of it. Seeing Sylvanas shatter the veil will likely be what breaks him, knowing that not only is his kingdom gone, but because of Sylvanas will likely never rise again.
My guess is that he is redeeemed at some point though. There has yet to be any confirmation on what exactly happens to the Forsworn, except the vauge hints of them succumbing to doubt, which should be reversible.
Difficult to say what could happen though, much of it depends on what they do with Arthas.
If Arthas is shown as iredeemable then Uther might be stuck as a Forsworn, but if Arthas gets a redemption arc then Uther will regain his faith when he realizes that Arthas could be saved despite his doubts.
On to different models though, i do wonder where Tirion is. I cannot imagine he would end up anywhere other than Bastion to become a Kyrian. I know that the reason we don't see him is likely to prevent oversaturation of Alliance paladins there, but that isnt an in-game explanation for where he is.