Aside using breath it’s really easy to overcap runic power for frost, why? Because too many abilities scale from runes rather than both. This is a problem.
Pillar of frost, scales with runes, and if you have obliteration, and you get obliterate and howling blast back to back, it’s basically really really easy to overcap, and to overcap is the correct choice, because potentially wasting the rime proc, and using frost strike will deal overall less damage than using blast, this counts double because blast will increase your strength inside pillar. But this alone would not solve the problem with rime, it should also stack to a max of 2 charges. Or maybe, during obliteration howling blast could use from 0 up to 25 runic power to deal extra damage. This would also avoid not having runes in the middle of obliteration, because you got howling blast obliterate back to back. I mean, it would not guarantee it, because it’s still somewhat rng, but it would certainly diminish it.
Remorsless winter is the same. You want to use as many runes as possible because they are the only things actually increasing the duration.
I think you get the idea, i would personally split the scale, reduce it, but make it apply to runic power also, this way you won’t be overly punished for using runic power when you “could” In theory use runes, even if it meant overcapping.
Increasing the cost and damage of runic power spenders is not really an option in my opinion, the problem here is not the fact that “too many” resources are generated, this spec can have downtime even if it’s pretty difficult. If this spec has downtime it’s because it either generate so many resources that you cannot spend them all in a normal gcd, or because the resource generation is spiky and then it settles down, in case 2 it’s possible to overcap, but it’s also possible to have some downtime.
Aand the answer is number 2, but then we have to ask, why is it spiky? And the reason is what i explained above.
The problem here is purely mechanical.
Frost is still a nice spec, but this is clearly a problem that should be solved.