Ability Points aren't really as abundant as you're indicating. Especially not early in the game where talents like All Skilled Up/Scientist are meant to be applied.
You have 49 ability points or 51 with All Skilled Up. If you wanted three max rank skills (Which would be a pure specialist build) you are left with either 4 or 6 points remaining. Presumably you want at least one level four skill with two max skills which leaves you with 9 or 11 skill points remaining; this means that All Skilled Up is either a 50% or 22% increase in your available flex points. Similar with Scientist in that it opens up more flex points for diversity or the potential for some splash + an additional 3 point skill.
Anaconda is worth functionally 6 ability points in that it can give you a 10% damage bonus on an already capped weapon type. There are two handed blunt weapons they are just extraordinarily rare because of how powerful they are.
Know it All/Bigger and Better are perfectly balanced. Those are some of the strongest talents in the game. This feels like an attempt to create overpowered talents here.
Courageous is an interesting case. Should you really consider traits when balancing talents; that's an implication that everyone is expected to roleplay a specific way for ingame benefits. Perhaps give it a little bump like Immunity to Fear and +1 initiative.
Elemental Affinity is very powerful. You are underrating it entirely and it's not situational so much as dependent on your tactical playstyle. It's just not a low level talent at all. More of a capper. Same with Elemental Ranger. Are you just not using a field creating mage/ranger? If you cover the battlefield with elemental effects rather than avoiding them out of fear of chip damage then these talents have different valuations. Don't assume your valuation based on your tactical plans is a global valuation.
Light Stepper gives 2 points of perception for the purposes of trap finding. Of course your valuation of -one- stat point is already skewed based on your prior evaluation so it makes sense why you wouldn't value two points for a specific application (It's also possible you don't value the ability to find traps highly at all)
What a Rush is much better than you're giving it credit for. If your team has overall high initiative than most often you will begin turns at low health. It's the reverse of some of the other talents: This is only bad if your team is already poorly constructed. It gets better the higher your team initiative becomes.
You also forgot Weatherproof which is extraordinarily situational and minor in effect. Compared to the air capper talent of Lightning Rod the remaining mage capper talents are very weak.
i think its a misconception to think you need 5 in skills. you do not need above a 3 in most cases, really.
increasing your skill levels does not affect damage or do anything for you except allow you to use high level skills without an AP penalty. There are very few high level skills worth using in this game.
there a few exceptions where a 4 would be nice, but even less where you would want a 5. the only reason to get a 5 would be to get an overpowered talent.
mages are somewhat of an exception with their level 19 spells, but these dont come to the very end of the game and mages can ignore things like armor and weapon skills. even then, its the end of the game by the time they can be learned. i am sure you can get through the last 10% without those spells.
with that in mind i think talents that require 5 points in a skill should be quite powerful, because there is little other reason to bother putting that many points in.
i dont think nerfing WtS was the best way to go. I think they should have buffed the other options so people wanted to make 5 point characters. Making the 5 point talents weaker just means hybrids with 3 in everything rule the day.
that said, sneak and invisibility are the two most powerful tools in the game. with 14 int and glass cannon mages can end every turn with invisibility and completely avoid enemies fighting back. sneak can also do the same thing for less AP, but requires positioning to be effective.
you can make 2 lone wolf sneaks or mages with glass cannon to make sure they have high AP and after level 8 you basically become immortal. cast a spell or two, then cast invisibility to end the turn. repeat on next character. enemies will consistently skip their turns and just stand there and let you kill them.
considering that is a completely viable playstyle, i think you should be allowed to feel powerful if you go with a stand-and-fight playstyle.