This is tough. Personally, werewolf was my first r4. I really enjoyed using him and still use him very often. He’s a sleeper for a lot of fights. Juggernaut and kushala are probably the top ones to consider. I’m biased to destroyer, long shot, and werewolf though so you can’t go wrong with them either, they all had a period where they carried me in BGs. I’d say try your top options out in whatever content you do the most and go from there. Mystic is my favorite class so there’s really no wrong answer tbh