There are two types of online tier lists:
1) The tier list where the players are used to offline playing: This tier affect a player's execution & timing (for punishes, combos etc). In this tier characters like Kabal and Skarlet will obviously drop. (This tier list should also include what 2nd list below includes).
2) The tier list where the players are used to online playing (i.e their execution and timing are good). This tier takes into account mostly what tools of a character are boosted (i.e reaction/punish not possible due to lag), but completely ignores the "execution being harder" thing, poke out timing etc.
My online tier list (2nd type only):
S+: Kabal, Freddy
S: Kung Lao, Sonya, Cyrax, Reptile, Cage, Skarlet, Kenshi
A+: Ermac, Kitana, Liu Kang, Smoke, Raiden
A: Sektor, Noob, Mileena, Jax, Shang, Scorpion, Rain
B: Sindel, SZ, Baraka, Quan chi, Kano
C: Nightwolf, Stryker, CSZ
D: Jade
F: Sheeva