I am sorry but I did not read the full thread. I am just giving my two cents here:
A little bit of history first: the “casters” roles come from the role-playing games, which first were almost exclusively team games. The casters in their original design were never meant to be played alone. At all. They were only supposed to be support or dedicated characters who are added to a core team of fighters.
As far as I remember, the idea of self-sufficient, balanced-like-the-other-classes caster likely came with Diablo II or with similar games where the game designers bothered with the idea to have all the classes balanced for solo (to be able to play them all by themselves) and PvP (for the sake of the competition).
I find the idea of playing ARPGs in solo pretty… strange, I would say without sounding offensive, so for me the concern of having any class other than the usual fighter not self-sufficient enough by itself just sounds… strange as well. Your class is not like the core class? Well, guess what, this is a different class, so of course it is different!
Now if we stick to the standard like in Diablo II for instance that all the classes available to the players should more or less be equal as a matter of challenge and reward, I agree that there is something wrong with the casters classes. But if you really want to look into this, you will have to dig deeper than just into just the classes and the skills.
Second, some history again, but more technical this time: the developers of Grim Dawn are said to be among those who did Titan Quest. I can feel it in the game so I can believe it with no problem as far as I am concerned. What about Titan Quest? What about the casters? Well unless I did pretty bad with them, I found them to be pretty meaningless until level 40 or 50, where you could finally find the first items to reduce those damn cooldowns. The magical attacks with no cooldowns did not exist in Titan Quest, at all, so your only way to play a real caster in it was with nothing else that your f####g staff until you could finally equip something with some cooldown reduction.
So now I am reaching my conclusion: casters are not meant to be played by themselves or as themselves in Grim Dawn, they are only meant to be mixed with melee or ranged fighters. If you play Titan Quest or Grim Dawn, you quickly come to that idea that the game is mainly designed for those feelings and those mechanics that you have by playing melee fighters. The game just feels right for this. The casters masteries in my opinion are only here to either give the impression of choice or to enable hybrids, ie different ways to play your melee or ranged guys.
Don’t believe me?
Well just take a look at the gear available for your characters.
Where are your pure casters items?
One way or another, you will end up with a character handling a mace or a dagger or a pistol or some other physical weapon.
So where is your pure caster?
There is no pure caster. There are only hybrids. This is Grim Dawn, this is not Diablo II or World of Warcraft or any other fantasy games with fairies and girly effects all over the place. The magic here has something weird, evil, from another world. Don’t expect here the same “magic” that you may have found in fantasy games.
Although Grim Dawn does much better than Titan Quest on that matter, it is still not really designed to solo pure casters. Either play them in team or understand that their skills are only here to improve the core classes. They are great in team with the right teammates.
Oh and one last thing: don’t expect much that having good casters will then make the game balanced and fair and right and all: If not done properly, a rework of the casters in this game or the addition of a real super caster could make all the core classes look like junk, joke, waste of time, and the trouble at the end would even feel stronger for the community.