How could you possibly make him any better of an assassin without overpowering him?
catalytic smash popup+dreadwind= death or crossblade+catalytic smash with a certain helix choice gives you a stunned opponent that you can pretty much basic attack to death and save your dreadwind. Rath is just as good as he needs to be. He catches you out of position and you die. Anything more for an assassin is OP
Crossblade is actually great as it’s not actually intended to be a big damage dealer. It upgrades to having other properties for a reason and it’s not hard to hit, it’s pretty big and moves in a straight line.
Nothing lackluster about the second spin attack given that his primary attack does good damage. If you get his stun combo through the helix it’ll make a notable difference in damage when you have a second spin on your primary attack combo and your opponent has to sit there and take the extra hit. (also keep in mind that it’s not all about killing other players, the extra spin is obviously extra damage to bots)
The double jump is good for being able to reach opponents mid air after a catalytic smash popup. Gives you a few extra hits being able to reach them as they’re first popped up. Also I HAVE been in situations where it’s either helped me escape or it’s helped me get a kill because I used it to reach someone who thought they were safe. The double jump throws off peoples aim because they don’t expect it. Everything has its uses
Leaping catalytic smash is obviously good for closing in and good for ensuring you can reach your opponent to get the stun after a crossblade hit if you chose that. I’d prefer more mobility over a blind unless I’m getting into team fights and I just need to disrupt someone, which you shouldn’t be doing much as an assassin anyway so it’s pretty situational.
Everything else is fine as well. I don’t have every mutation so I can’t speak on them but not every helix upgrade needs to be some super power up, some are only to be used for certain circumstances but everything can be useful.
IMO he’s fine as is, he already own everyone 1v1 which is his job