Hypothermia vs increased critical damage vs increased critical chance.

I'm building a crit glacial cascade witch working off health and Eldridge battery. I'm currently looking to optimize the 6th link for my GC. Atm my link setup is glacial cascade linked to faster casting, spell echo, increased area effect/ concentrated effect for bosses. Most of the reading I've done shows added chaos as the best 5th link and I'm tossing the idea of hypothermia, increased crit damage or increased crit strikes for my 6th. Wondering what would be the best incense to my overall dps.

hypothermia gem gives additive damage so it's unfortunately not that great. i'd go with the crit gem personally.

I can't give you a 100% answer. I may be able to help you choose though.

Hypothermia will only increase your damage on the second hit. So as long as you are not one shotting, hypothermia will increase your damage.

Increased crit damage will make it more likely you will one shot. It will increase your damage variance.

Increased crit strikes will lower your damage variance.

I always felt the actual crit chance you strive for is personal preference. Get to the crit strike chance you want, then put everything else into crit damage.

You usually get doublehits with cascade, so if we assume two casts per kill, which is four hits, it's ~30% more dps from hypothermia at L20.

If you're real heavy on crit you might not get as much from crit supports, but if that's the case you also might be oneshotting too much for hypothermia to do anything.

I'd probably slap on a tabula and give both setups a go, that's what the thing is for. If you can't notice any difference just go with the gem with the easiest color to roll on your chest.

Depends really. Although the damage effectiveness is only 60%, its effectively double (2 hits per cast). So, it might even be added cold (This scales with any +cold damage nodes you most likely have). You could always calculate what gives you the most DPS increase, although this isn't necessarily the best option for clear speed. Cold Pen works well against bosses and things with resistance, and with freezing things. Bigger hits mean longer freezes/chills. So, hypothermia is likely the best option there.

Like raics said, get a tabula and see what you like.