Most challenging and wanted DPS class?

[Llugen]

Only read the OP, but NIN is generally the most desired DPS class by all other jobs, mostly for Trick Attack but also for Shadewalker/Smokescreen (and even slashing if you're running PLD/DRK).

Most DPS jobs aren't particularly complicated by design (and a big bullet point for Stormblood was to "simplify the rotations/complexities of jobs", which has succeeded mostly), and I don't have NIN to 70 so I can't really speak decisively about its complexity at level 70, but if you want a job with tons of timers management and a lot to think about, I'd recommend SMN.