I actually dislike almost all of the custom spells and changes to existing spells. Almost none of it was needed, not sure why it was done. Any work on skills should have been done the same way they already had done in Korea.
Taos on here are absolutely nothing like they were on any official server.
Warriors are very different and I don't think the way they are here works, at least not in the way it was intended. Warriors were meant to be the tanks from reading the features and the original discord, that along with the AI changes could have been a good idea, just executed badly and I think backfired a lot.
Wiz is kind of in the middle, they have some of their better skills like renounce to early on, lost some of the later ones like Mirror Image, shield is probably OP. Removing flinch screwed up a few things too, like Judgement of Heaven is a Wiz retreat tool, you get attacked they get T-Bolted and you have time to get away.
Assassin is incredibly complex, the GSP version of them and the original Korean implementation was so overpowered it wasn't even funny. But they were developed to compete with a player base that was already reaching level 80. The rebalanced version of Sins that exists in Korea would have worked a lot better here.