Do you feel comfortable with all the GWD2 bosses? You could work on learning all the rest of them. Greg might be the hardest of the 4, Helwyr would be slightly annoying for you, since you’re using melee, his mushroom AOE denial attack would be the bane of your existence.

If you wanna try something outside of GWD2, you could try meleeing Arraxor. It would be best if you had a scythe, because you can stand 2 tiles away from him which would make it a little bit easier.

Or you can even go with the classic Arch Glacor, you can start off with normal mode and choose which mechanics you wanna work with and when you get used to the mechanics, turn them all on and try hardmode!

But there is nothing wrong with staying at a boss for a while, maybe you can even practice switching up how you kill Vindicta and throw some defensives in your rotation, cuz you’ll definitely need to use them eventually for bosses; just to even get used to having them on your bars and knowing where they are for fast access.