Yeah tbh
I think Tangrowth is either A rank or B rank I'm doing a grass run atm and Tangrowth has been the MVP of the run
with Giga Drain, Ancient Power, Growth and I would have loved to have Knock Off but I have a minus attack nature
does damage to almost all the leaders that I have faced and not to mention that Tangrowth rarely gets 2ohko by any Physcial moves.
The only down side is the SpD anything that runs something special does a lot of damage to it.
Tangrowth should be A or B rank merely for the Bulk and that you can run mixed even with a minus Attack or Special Attack Nature
Moves Knock Off, Giga Drain/Powerwhip, Growth, Ancient Power as main moves but you could run the Powders moves also