A point that I want to make is Icecap vs Avalanche. All guides suggesting Ava over Icecap due to it's raw damage contribution but talents like Gathering Storm/Frostscythe/Glacial Advance/Obliteration has indirect syngergy with Icecap.
Icecap increases the Pillar of Frost buff uptime therefore increasing the damage contribution of these talents.
More Frostscythe during pillar, more damage from Fscythe.
Having 2 Pillared RW in a minute instead of 1, net gain to RW and even further to GS talent.(around %20 crit levels)
Glacial advance is similar to Fscythe, although It competes with resources in a negative way for Icecap to benefit.
Obliteration is similar to RW/GS. Especially around %20 crits I consistently reduce the CD of Icecap to 40ish seconds which helps me do alot more damage with RW/Obliteration.
but the guides that I came across don't pay much attention to this. I do not have any math data with me atm for the current situation to make a solid comparison but I forsee Icecap gaining more over the course of expansion due to the abilities that It effects tied to the weapon damage and higher AP% compared to avalanche's flat AP damage.