Gauge management in FFXIV has been reduced to "Should I use this now or save it?" That's the extent of the decision making, and even then it really only necessary at the highest level of content. If the complexity of a job only shines through in the bleeding-edge of content then I would call that poor job design. I'm not even sure why gauges still exist because functionally they all work like a stacking cooldown. This isn't unique to Viper though. It's a problem for every job with a gauge.
Honestly this is a really poor excuse for boring job design, and if the devs were to give an excuse like this my response would be that they are no longer fit to develop the game and it needs to be passed off to a different team. In order to make fight design more fun you don't have to dumb down job design. That doesn't make any sense.
There are several examples in the MMO market of games which have both increased the class complexity and fight complexity over the years. In fact there is one on the market right now in which you can go back and actually see what the game was like when it first launched compared to today. WoW's combat design, for both it's classes and it's fight mechanics, is almost unrecognizable currently compared to the original version of the game in terms of complexity. It's current fast-paced combat, with it's quick GCD and reactionary gameplay, is such a far cry from the single-button slow-resource-building 2.5 GCD of old.
On the flip side I would argue that FFXIV's job design has actually been in regression. Any semblance of reactive gameplay has been stripped away. Resource management has been reduced to what is functionally just another stacking cooldown. Every single button press you make is pre-determined. As before this is not an issue exclusive to Viper, but Viper is just the most recent example in a long line of examples.
TL;DR Job complexity and fight complexity are not mutually exclusive. Both can be made interesting simultaneously without sacrificing one another and a skilled team would be able to do both.