As a mage on my main, and having played with a dozen other mages... I can tell you since the flux nerf the money making potential is CONSIDERABLY less than of say a straight melee toon or a MA. (Both of which I have either had or currently have as alts).
In one hour of farming earn between 100-200g from bandits, risars, or even sators. If I go after a bit more challenging things like Tagmatons, or Trolls I can easily double that. This is with a MA or my MC/Melee toon.
My MM can make about 70-80% of that mainly do to casting times being slower than plinking away with a shortbow and weakspoting every other hit.
As a spiritist you average about 2-4 cuprum flux every hour, maybe 2 silver and if you are lucky a single gold. But 9 times out of 10 you wont get near that. Then you have to try and sell those on the broker, the broker that is already flooded by people who have stockpiles of flux from months ago. Now you could say you are farming spirits to sell... even that isnt a huge earner, you are making 3-4g PER small spirit box, and 10-15g per medium. They are not HUGE sellers by comparison of other items.
The payout vs investment in the character build doesnt even come close to balancing out on a Spiritist currently. You are looking at spending 12k gold for the two books needed on the broker. If you farm them, you will need a pretty good group, of between 5-10 people. And there is about a 1 in 8 chance of you getting the drop you need from either boss. Which means you will need to spend hours on farming that boss just to get one book. These are two bosses that are relatively popular spots for PVP because of their value in loot. So expect your 5-10 person group to get zerged down by a 20-30 person group.
This compared to Necromancy, the other "rare" magic school. Which you can just head to a "hidden" vendor and buy a set of notes for 10g, and unlock the skill, or buy them off the broker from 40-100g. And then spend a few hours in a house grinding the skill up with some ashes and ritual blood from a few stacks of ritual sacrefices. Not exactly the 12k gold investment of Spiritism. Hell even if you bought the necromancers tome off of the broker it isnt even 6k gold currently. Now the REAL money sink in necromancy is Rituals if you you choose to do it. It is not a requirement to be a necromancer, unlike portals for spiritism.
And this is what brings me to my final point. Spiritism mainly portals needs an entry level scroll like necromancers notes to get started for a more reasonable cost. While you are losing the skill from the book in exchange for the grind you are paying considerably less.
I 100% agree that portal magic should have a cheaper alternative like the necromancer notes, Maybe not quite as cheap, but something easier to get at least. Though, lately, the price of multiverse and that has been dropping fast. I got multiverse lore for 3,100 gold not too long ago. Still a huge investment at 6-7k, but not the 10-15k it used to be.
As for the "farming", I would still say it has a valuable place, because it is essentially risk free. Farming in meat mode, I almost always run into at least one other person or group, which 50/50 on whether it turns into a fight and as a mage I'm more than likely going to lose if it does. Outside of a couple of more popular locations, the odds of running into another spiritist while farming spirits is extremely low, and the risk when it does happen is even lower.
In the example you gave for flux per hour, even if you only got a single silver and no golds. Selling spirit boxes, 3 cuprum, and 1 silver. That is going to net you around 350g. Maybe more, sure, other methods of farming can make more. But they are significantly more risky, and the risk increase for the additional gold is, imo, not really worthwhile.
200+ gold per hour with no risk at all is a reason to have it, and I know a couple people who only keep it because of that, and the ability to even easily traverse the map or transport gold at lower risk in the form of spirit boxes. To use the words of a guildie, "Spiritism is easy to zero to hero your way up in a town where you have nothing."
All of that said, I think spiritism needs heavy reworks, as I stated in my earlier post. There is a lot of room for improvement, and things that could be done to make it more interesting and enjoyable. And, with only three schools of magic in the game right now, none of them are truly "rare". Given enough time, everyone that goes full mage will eventually try out portal magic, because there just isn't anything else for us mages to do right now, and that quite frankly sucks.