Guinevere is still one of the most used tanks in the game, as far as raids go anyways. You can check out the most current positioning report in Titan Mafia for Razors and co’s work, and you can check out the official game data for this past years Raids Index 🏆 Heroes Hall of Fame & Stats! and see that Guinevere is one of the top 3 tanks there.
I can’t speak for how the future meta will shape up myself, though I predict Black Knight will join Guinevere and Kunchen up there in the top tank spots. But I’ve yet to see a disproportionate balance issue myself with the new introduced heroes.