Tangrowth should drop to C+ in my opinion.
The defensive set is pretty much outclassed by the likes of Amoonguss (and Roselia to a lesser extent) who has waaay better typing (let's it wall Hitmoblee and absorb Toxic Spikes among others), mixed bulk that more than make up for the slight loss in Defense and offensive sets are mostly outclassed by Virizion, Rotom-C and even Sceptile (who prolly needs to drop)
I also support Volbeat being added to D as I have used with great success as a rain setter and, while it is pretty much outclassed at doing anything else the fact that it can repeatedly set up rain on troublesome Grass-types and the added bulk that let it take on shit like Hitmomlee ok make it worth of a ranking of some sort.
The defensive set is pretty much outclassed by the likes of Amoonguss (and Roselia to a lesser extent) who has waaay better typing (let's it wall Hitmoblee and absorb Toxic Spikes among others), mixed bulk that more than make up for the slight loss in Defense and offensive sets are mostly outclassed by Virizion, Rotom-C and even Sceptile (who prolly needs to drop)
I also support Volbeat being added to D as I have used with great success as a rain setter and, while it is pretty much outclassed at doing anything else the fact that it can repeatedly set up rain on troublesome Grass-types and the added bulk that let it take on shit like Hitmomlee ok make it worth of a ranking of some sort.