Shandera has good defenses with Low HP, poor attack, and mid-level speed that allows it to outspeed a majority of the slower tanks. However, the one stat that immediately jumps out at you is the 145 Special Attack. Shanderaa now smashed both Alakazam and Porygon-Z for the title of the highest non-legendary Special Attack stat by 10 points. There are extremely few Special Attacks that can feasibly do that with that little set up. If Flash Fire wasn't a good enough ability, it also gets Shadow Tag from the Dream World.
However, the downside is that Shanderaa has 5 common weaknesses: Dark, Ghost, Rock, Ground, and Water. This leaves Shanderaa not only Stealth Rock weak, but Pursuit weak. In addition, Shanderaa doesn't have Levitate, unlike Rotom-A, which means it is susceptible to Spikes and Toxic Spikes. In addition, it is outsped by a myriad of new and old threats, starting from Gyarados and including both new Dragons (Ononokuso and Sazando). This is slightly crippling, although I expect Shanderaa to be used as a weapon against stall mainly (as if we needed more), instead of against faster offensive teams.
Is Shandera viable? Yes, on the right team