Major Brittle is similar to EC in terms of effectiveness, giving it too much of an uptime would be gamechanging. 7 seconds is a good place to have it, since the effect applies at 2 seconds into the 6 second AOE and does not get extended- leading to a 26.6% uptime on Major Brittle, meaning around a 5% average crit dmg increase.

Allowing Major brittle's countdown for targets to start after leaving the area of influence of the icicle would be a good start (this would probably extend the duration by 3-4 seconds). Alternatively, they can just make the duration of brittle longer (7 seconds seems fair, and makes it comparable to Archdruid Devyrick in terms of raw effectiveness), and seeing how the effect is completely avoidable in pvp I don't see how this would be much of an issue.

Alternatively, would it be too much to have there be a 5 piece set bonus or non-helm/shoulder mythic that extends duration of effect on ults? Having 1 monster set rely on another is a bit silly. We have Archdruid and TT which have the same debuff but different proc conditions, why not have Nazaray and some new set?

With the current crit damage cap, there's not really any need for Major Brittle in organized groups. Even if the group needs it, its not a massive DPS buff, giving around 6-7% DPS from the 20% crit damage (about 1% better than Major buff sets like Olorime with Courage).

The similarity to EC is notable, and EC gives 75% of the effect (15% vs 20% crit damage) at an easy 100% uptime. It seems fair that Nunatak could give 75% uptime then, to be in-line with the other crit damage buff set.

I wonder if Arcanist will have a way to apply Major Brittle. If so it could end up replacing the EC necro in groups.