I really think rotom heat should be higher. It can take on almost half of everything in A, either walling or OHKO-ing them. Landorus is shut down by hp ice, heatran and Tapu koko literally cannot touch it, as well as Celesteela, amoonguss, megazard and salamence, minus Draco meteor. Aegislash is OHKOed as well, I believe, although I have to do some more calcs.
Pyritie i would like to point out that a new and upcoming 'core' on high sd ladder is zardy, koko, kartana with snorlax, cress, and lando-t. Snorlax does indeed hit hard and has potential, but its bulk is lackluster compared to vgc17. It requires way more support then last year, and it either needs a dedicated team or 2-3 mons with specific movesets with moves such as redirection/ally switch to do well. It should really B+ rather then A-, as the mons in the A- tier aside from lax require substanially less support if any at all to properly function on teams. The kartana on this team is believe it or not a twind berry set. Also Stakataka shouldn't be B+, it should B-/B. Compared to the other mons in the B+ tier, it is much weaker and requires much more support.