I’m also hesitant to level my dinos because Ludia likes to nerf. Sometimes I think they do it intentionally under the guise of listening to other players’ cry for nerfs because by nerfing a dino, it forces other players to spend on leveling up other dinos so it actually is in the their business interest to do so
Anyway, these days I find that if I do want to level dinos, I level the “movie stars” of the franchise like IRex and IndoRaptor because they are unlikely to get nerfed. I also level the strong dinos that players don’t get to see as often in arenas. For example, people complain about Stegodeus because it gets overleveled and used a lot so there are more players exposed to it. However, Ankyntrosaurus is actually even more of a pain yet because of its rarity, not that many get exposed to her so less cries for nerfs. In cases like this, if one has the dna, she is a much safer one to level unless you want to go for Tryko.