A ---> A+
With Cobalion gone, Durant is back to where it was before as a wallbreaker. It sits in a great speed tier, has multiple sets that work, and hits hard, even on resists. While it still has problems that it had before, like being easily beaten by Emboar, and Hustle missing at the worst possible times, Coba leaving makes Durant's job easier.
A+ ---> S
A more controversial nomination but I think Tyrantrum deserves S. It hits extremely hard even without CB, while it can patch up its average speed with Scarf. Has a good matchup against a lot of the meta, especially with Cobalion no longer being able to come in on a choiced STAB move and set up SD freely, so it can work as a revenge killer. It has enough bulk to take hits as well. Tyrantrum is amazing in the current meta, and on the level of the other S ranks, at least in my opinion.
A- ---> A/A+
Supporting this nomination, as both the Specs set and the Scarf set put in work, Specs tearing down many walls with a powerful Leaf Storm, and Scarf being a great revenge killer.
Stay A+
Doesn't face competition from Cobalion anymore with SD set, though other sets are outclassed by Tangrowth.
Also, what caused Magneton to drop to C+?
EDIT:
Another nomination
Unranked ---> C-
If Victreebel is ranked, than this deserves to be ranked too. Even outside of sun, Exeggutor is a great wallbreaker, but in sun, Exeggutor is great. Still has its flaws, but it at least deserves to be ranked.