@LordThundyr Good start on a Cold FOI MH build! I haven’t made one yet, but I would suggest getting Murmur as others have said as well as checking out a relevant build by @Nery here:
Although it’s for PRM, the skill choices will be pretty similar and most of the itemization/Devotions are applicable as well. Using the Rimetongue chest would increase your FOI damage by moving a significant portion of the Lightning Damage to Cold. Also, using the Scales of Beronath could be an option for a belt. I think if you get more Cold damage converted, grab more RR and swap out all that DA for quite a bit more OA (plus more crit damage) you could kill faster and get lower times in the end.
@Cinder’s suggestion of Chillheart would be awesome as well combined with the Rimetongue Chestguard - almost full Lightning to Cold conversion then… Just need to grab more cast speed elsewhere.
Just my 2 cents! 