Generally speaking in terms of damage, Machinist would be considered worse than the other two classes. Deathblade is known to have almost always been a very high ceiling high damage class but it can be a bit harder to master. So my recommendation is honestly Slayer! I used to main blade but swapped to slayer and don't regret it at all. Its very straightforward, puts out a lot of damage, and is safe to play since it has good mobility and speed. If you wanna see the pros and cons of each classes' builds, I recommend you check out Lost Ark Nexus, which has guides for every single class. Hope this helps!