Regardless of how targeted the summoning stones are, they are still available in quantities of 12 per week from dungeons. Assuming they would still keep their same targeting function, 2 per week. If you needed extra copies of a specific common, and these stones just straight up got you that common, you’d still need 95 weeks worth of stones to get that one common to mythic. Alternatively, you can just do what you did before and drop about 24k gold keys the week it is released, assuming they will still be given in such quantities where this is viable. If it is about unlocking your first set of commons, well, good luck clearing dungeons, or even reaching Drifting Sands for that matter. A few hundred gold keys will unlock the common you need, a few thousand will get the first few ascensions, and beyond that, you need a ton of that troop for it to be relevant. Since 99% of common troops will still come from gold keys, this is not enough to change the direction of the wind. And yes, you can use shards to craft some jewels and then craft more troops to correct a slight imbalance, but at this point, that looks to be the worst decision you could make in soulforge outside of turning 10 diamonds into 100 souls.
If you are targeting something of higher rarity and a specific color, well, good luck with that even if there is only one troop per rarity tier in the drop pool at a given time. Even just getting one copy of a specific ultra-rare if you could choose which drop in the rarity teir you want could potentially take weeks at 4 pulls per week (assuming both colors). The way these resources are currently handed out, this solves absolutely nothing even if they were more focused. I highly doubt drop rates for summoning stones will exceed that of level 3 guild keys, but time will tell.
To reiterate on what @jainus said, as a long term endgame player it is trivially possible to earn more arcanes per week than are required to trait every new release in the same time period through glory packs from the weekly glory. Color disparities matter, but over the course of years, these, too, dissipate, especially with short term needs having already been fulfilled through explore, I reached this point months ago. Playing at a certain level ensures you are always moving toward this point. Having a way to accelerate reaching this point may seem like a good idea short term, but long term, it will only have more players in the same boat we are in faster. But not much faster, considering clearing all the weekly dungeons amounts to either a celestial or half an arcane, which is equivalent to about 10 minutes of explore even at midgame, and 5 or 6 minutes on average at endgame, which you probably spent clearing the weekly dungeons in an attempt to get diamonds anyways.
Nobody expected this. I have said multiple times I expected a time component and an effort component such that the effort component (farming) would be the bottleneck and therefore the focus of the majority of people, while people sitting on tons of extra currently useless dead-end resources would need to farm less but would still be subject to waiting, possibly even having everyone start on equal ground with what the effort component was so everyone had to farm while that time gated component slowly accumulated. It would have made sense, for example, to have colored Jewels start appearing everywhere as drops, and needing a ton of them to craft a mythic in addition to much more “other” stuff that currently dead ends (souls, traitstones), with diamond requirements having been reduced from what they are now. This would have made the jewels both useful for a long term goal and available in usable quantities short term. It would make diamonds not stand out so much as the hard bottleneck, because you would still need to farm a bunch of Jewels while you are waiting for them to accumulate. If one or the other finished first, that is where monetization can come in, and would probably be looked at a bit more favorably. As things are laid out now, the only thing there is to focus on is the bottleneck, which boils down to a daily activity hook (which will surely get old, even if it is minor) and months of waiting.
