First off, such a tierlist is heavily dependant on your playstyle. While some skills are without a doubt objectively better than others, some skills are seemingly "niche", but can abuse the games mechanics to such a degree that it can be argued that under the right circumstances, they are god-tier (an example of this would be transmute terrain, that allows you to one-shot just about everything with lava or deathfog IF you have the patience for it). Skills like Reactive armor are not very good without a shield, but with a shield+fortify+bone cage+heart of steel etc, it certainly is above average.
Also, which difficulty? Some skills either gain or lose effectiveness depending on whether you play on the lowest or highest difficulty. Are we playing 4-man party, or 2-man party? That is relevant for skills that buff your whole team, as those lose value with fewer party members. Physical or magical party? Thick of the fight is indeed a poor skill for melee characters, but decent enough for a tanky mage (since, for some reason the damage bonus is additive for physical damage, but multiplicative for magical). Venom Coating and Fire Brand are good skills for a hybrid party, but is otherwise terrible. And finally, some skills are very good early game (or the opposite), but fall short later on due to poor scaling (such as the soothing and mending armor restoration effects).
There are a few outliers in the list that, during MY playthrough, should be much higher/lower up on the list:
Clear mind, for instance, is one of the best buff spells in the game (especially lategame) and clears one of the most detrimental CC's in the game (charmed)? B-tier --> SS-tier imo.
Bone Cage can easily add such vast amounts of physical armor during prolonged encounters that it trivializes almost any encounter, but is also B-tier? B-tier--> S-tier
Overpower is easily the best warfare skill in the entire game if you're able to ensure that you generally have more armor than the enemy, and play on tactician. And yes, I think it's even better than its closest contender, Battle Stomp. C-tier-->SS-tier
Chicken Claw is in the same tier as the "... Skin" skills? What? That skill is broken. C-tier-->SS-tier
Assassinate does significantly less dmg pr. AP than normal attack, except when you open a fight with it under stealth and have picked the otherwise useless "Guerilla" talent, but is the same tier as Overpower? C-tier-->F-tier.
.... and I could go on. I agree with the majority of them, but some of them make me wonder if we are playing the same game. But like I said, there are a lot of contingencies. Whoever made this list might have played the game on a different difficulty, using a different playstyle and team composition, that makes it impossible for us to agree under a common ruleset, and a list like this is tentative at best.
