SS: Strong in 4 roles and viable in every role.
S+: Very strong in 3 roles and viable in both other roles
S: Very strong in 3 roles
S-: Strong in 2 roles and viable in at least 1 other role.
A+: Very strong in 2 roles
A: Strong in 2 roles
A-: Strong in 1 role and viable in at least 1 other role
B: Strong in 1 role and decent in at least 1 other role
C: Strong in 1 role and not viable in any other role
D: Not strong in any role
A god's "strength" in a particular role is not dependent on their place in a typical Tierlist. Rather, it is determined by how effectively their kit can be fully utilized in different roles. For example, Zhong Kui is placed in A+ tier because his kit allows him to be fully effective in both mid and solo, despite not being a strong mid or solo pick at the current moment in the meta.
Erlang Shen is S+