Free Agent - NA
SS - Overpowered
S - Strong
A - Good
B - Average
C - Niche
D - Lackluster
Keeping it simple and broad. You can get away with a lot of nonsense in Casual games since people here usually play for fun. I'm not using the "+" nor "-" tiers because I think having a larger pool to view or see helps players not focus so much on a god's placing on a tierlist specifically, rather how they stack up against the pool of other gods. Matchups, as well as teamwork and individual player skill determine the game more than "I pick op god so I win", the game is much more nuanced than that.
With that being said, All gods in the higher tiers will tend to dominate games at early stages and their impact the map at a greater degree than ones in lower tiers.
ss
s+
s
Strong
s-
a+
a
Good
a-
b
Average
c
Niche
d
Lackluster