I think the positionals have their place in Viper. Unlike most melees Viper isn't a weaving heavy job with your only true weave being the end of your normal combo since the long CD attack has a longer GCD so weaving isn't really a thing since it's so easy.
Positionals make up the skill ceiling instead of weaving which I think is good for the job. It's not like it's incredibly positional heavy, it does less than Samurai and probably even Reaper per minute.
