While I understand the love for ice in particular many of the core concepts alongside elemental damage have been abandoned.
Iam still waiting for lightning or frost buffs akin to behemoth or engulfing flames and groups that base their entire setup around damage types.
Or perhaps something along the lines of the old dark-elf passive that increased fire damage by I beleive 7%~

I also find the trigger condition for sets like crimson oath or yolnakiin downright insulting. The set effect may aswell read "if you exist:"

Alas if it is any consolation iam sure the dev team thought it was great.

(For PVE)

i love using nunatak for vcr when we haven't reached crit cap. simple proc conditions and it works very well to CC adds in portal to prevent them from coming up top. it works really well on z'maja when major vuln as a debuff is covered as well as the pen cap are covered as she has a lot of invulnerability phases that make the downtime less of an issue. it's simple enough to use to debuff minis with as well. it has a 26.6% uptime on its 20% crit dmg debuff leading to an effective 5.3% crit dmg- the biggest issue is that the players on your team need to crit to see this benefit. by comparison, devyrick has a 46.6% uptime on its 10% debuff leading to an effective 4.67% damage increase- but this increase isn't conditional on critting. When looking at it as a trial debuff, it even surpasses a 62.5% uptime MK- the max possible (but only when the crit cap hasn't been reached). If your trial isn't running Kilt or can't, or EC is not covered, this is definitely a good option.

I posted all this because this is likely what the balance team is rationalizing when they consider the values. If we wanted double the duration upon application of the brittle for all, we'd probably get minor brittle as the proc. For PVE what is needed to really make this set shine is a body armor set or mythic that increases debuff duration if you ult, similar to nazaray. Alternatively, I also think there is room for improvement for Major Brittle to be a little bit longer, or to reapply its effect right after it ends if the npc is still in the AOE.

In PVP-
Major brittle in PVP should not have to proc after standing near the spike for X ticks. It should proc after X ticks of the initial nunatak stack getting applied regardless of the immobilize unless purged.

Right now the design is to apply nunatak and then lock them onto the spike with other hard CC/pulls- it would be much better if they just needed to get hit by the spike once to eventually get major brittle within a couple seconds.