Specifics have changed, the core character is still there. New New Trundle was also driven from his people. He was introduced from his recent situation, his childhood could very likely be similarly "tragic", that story just hasn't been told yet. Etc, etc.
New Trundle was a physically inferior challenger to a weak leader, although he is athletic-looking next to a human. He was always a physical character, just goblin-ugly. Now he represents a physical troll-character visually. He is also much more part of the world and now you could imagine him being relevant to the overall story or lead his own stories; old Trundle was very one-off.
Biggest difference is the old one left his tribe to die, the new one came back to lead them. There was the rotting curse-motif, but that was a questionable theme for Trundle specifically, I think. It has more potential elsewhere.
I don't think the core of new Trundle is very different, he is just reiterated; you are clinging to very specific, subjective ideas about the character. The core remains, as I have said. Specifics will change in development.
I'd rather have things change and be good than everything staying the same just for the sake of it. Some will cling to the latter I suppose, but you should think about it twice before you do.