These two dominate the tank line-up. With the tank meta in full force these champions are very reliable with good CC and other tools.
Maokai and Gragas' nerfs dropped them a tier but still very strong and reliable picks. Elise is the best choice for a damage jungler this patch and for the past few patches.
Zac got nerfed pretty hard so he dropped down two tiers. All the other champs have been performing well in solo queue and competitive play. Kayn is S- with the Rhaast form. Jarvan has rose this patch although he is an AD Bruiser. He's good because he can still be a tank. Rammus and Rek'Sai are slightly underrated but they are good picks in this tank meta.
Nunu lacks much utility to be in higher ranks however he is a tank and is good at securing objectives with Consume. Hecarim just got buffed this patch and I think it makes him viable at high level play again. People just haven't realized yet. Kha'Zix kind of fell down because of the meta shift. Carry junglers are not as favourable now. Shyvana is a hidden strong champion because she is good at bullying tanks. Warwick is just a good champ with good bulk at insane mobility.
A lot of these champs fell because of the meta shift (Graves, Ivern,Jax,Lee Sin,Nidalee,Rengar) they simply aren't tanks so they are not the best in this meta. Dr. Mundo however just got a decent buff and he has moved up several tiers. Olaf in general can be a tank but he is just in the shadow of some others champions that do his job better. I like to think Skarner is a hidden OP. He was picked in Korea a few times as a curveball pick and he performed well. Vi also received buffs this latest patch and I expect to see her more often in Solo queue.
Amumu is a tank but he is easily countered. Evelynn, Kindred, Master Yi and Wukong are not tanks either and are even outclassed by the champions in the tier above. Trundle is fairly popular in Korea but mostly Top but he's still not a bad pick. Volibear is just a worse version of Maokai, Sejuani, Rammus and Gragas.
Overall pretty weak picks. Not much to say really.