Despite monolith being out for some time I still feel hesitant to say that this tier list is "completed" so to speak. I think that a lot of heroes have untapped potential or have yet to have counterplay developed to them. To that end a tier list will always be a work in progress, and once again this is mostly my opinion so take it how you may.
High damage output paired with innate tankiness and a second life make Greystone extremely difficult to deal with.
Excellent damage combined with high utility spells and amazing area control/denial.
Strong damage output with amazing pick potential and high health pool with Siphon stacks.
Extremely strong ultimate that can destroy enemy carries. Force shield is incredibly useful in standoff situations.
In-kit armor shred and a global ultimate give Murdock strong presence in the mid-game.
Best attack speed scaling of any ranger gives Twinblast extremely high damage output late game.
Strong poke and team utility. Has access to good cards because Order/Intellect affinities.
Brings a lot of crowd control to a team as well as an ultimate that combo's with more than half the cast in some way.
His rock is probably the strongest CC in the game. Performs well in jungle, offlane, or support.
Thunk is incredibly fast and Narbash has the only in-kit healing. Has good peeling potential with his speed up and ultimate.
Feng Mao -
Has strong chase and dueling potential, and his kit offers a little bit of everything.
Amazing chase and pick potential, but doesn't offer much in teamfights or if he gets behind.
Offers solid damage and some CC, but may struggle to find good engages.
Small AoE poke and his ultimate requires him to be close to the opponent. Has high maneuverability with torn space.
Offers strong global pressure with her ult but doesn't have any reliable hard CC in her kit.
Potentially strong pick but relies on getting ahead and may struggle in teamfights.
Lower overall damage output than Murdock or Twin, but can still succeed with a strong support.
Damage output is still a bit on the low end, but can do amazing if she snowballs.
Her spells require her to stand still and her damage output is lower than other mages. Offers good CC.
High damage output but doesn't have a reliable gap closer. May struggle with mana.
Lt. Belica -
Low damage scalings and doesn't have a strong poke tool like other mages. Her ultimate is situationally amazing however.
His RMB gives him a ton of armor and he brings strong burst damage but doesn't do as well as other fighters.
Below Average Tier
Landing hooks can be difficult with the updated movespeed and he is heavily punished for missing abilties.
No form of self peel whatsoever. Her strongest asset can't be utilized very well in the current meta.
Suffers from many problems, has low damage output and is squishy. His primary ability gives the enemy CP for essentially free.