Personally, I think the core rotation is really fun and the visuals are great. But it has literally nothing outside that rotation except Slither and role skills, which is kinda boring. No defensive ability or heal, no group buff, no utility, no resource charge for downtime.
Compared to something more recent like Reaper which has all of those things, it seems kinda… sloppy.
Currently, it doesn't even have the damage output to justify that single-mindedness.
It also makes solo content a real hassle; something DPS jobs already struggle with.
It even has various animation oversights, like the sheathed weapons not shifting when sitting or mounted to avoid clipping, the combined form having no super-sprint animation in CC, no altered sheathing/unsheathing animation or alternate pose.
The combined form itself appears to be a tacked on relic of something they decided to remove late in development.
It also suffers from starting at level 80, because they felt the need to give it the bare-minimum number of skills at that stage to avoid overwhelming players when they pick it up. This means the Viper gets royally screwed by the down-leveling from roulettes and fates.
Like I said though, the rotation is really fun at least. All the issues I listed aren't exactly huge. I'd say it takes the job from a 10/10 to more like an 8/10.