[Shujin]

Insulate is one of the most rarely used skills in the game, for good reason. It doesn't do all that much to help you and most of the effects are counter acted by itself.

Lets break it down.

-10 FP
-1 Ally with 3 tiles gains +30% Ice resist 
-3 rounds duration. 
-You won't trigger ice tiles by walking on them. 
-Cures/Immunity for Frostbite during the time.

Okay the first big issue is, that its only 3 rounds. Thats very little time to make use of it and a Winterbite as counter makes them always win the Momentum Trade off.
The second issue is how weak frostbite as an effect is to begin with and how little a MA cares for Ice tiles. Shukichi? Yeah ice tiles don't matter.  Getting pushed over a line of ice tiles? the absolute strongest frost bite effect is level 50 (60 with spirit), tied to an invocation, with how damage tiles work now its not all that scary at all. Most people have plenty of ways to get around ice tiles, teleports, attacking skills that second as mobility etc. So not even as a team action useful outside of ice resist which may or may not be helping. It doesn't help that ice point greaves is also already doing the ice sheet thing.
This makes it a very easily to miss skill, because Verglas is already very skillpoint/skill slot heavy class.

Suggestion:
Insulate
- 30FP (-5FP per rank, so basically the same as now +10)
- 1 ally within 3 Tiles
- Rank*10% Ice resist
- 3+Rank rounds (Or 3+Permafrost rank.)
- Won't trigger Ice sheets (I honestly think this one is weird already, Ice point greaves does that already, and is so much more useful)
- Cures and grant immunity to Celsius OR Frozen even. (up to Frozen level Rank*20?)

Bonus:
If Ice Point Guard is active: On being attacked deal Rank*5 Protection Ignoring Ice damage, double when guarding. OR gain 5*rank Magic and/or Physical armor.
If Ice Point Greaves is active: Ice Skate costs only 1M (refunds 2). OR while Standing on Ice tiles grants you +rank*5 Evasion reduction.

Bonuses are just some ideas, cause I feel it could need a little extra for Verglas, without making their normal damage output too silly or support the tank SWA style too much.
certainly Open to other ideas. Maybe having ice point guard active could just make it refund 2M? Making it a solid quick cast protector.

[Autumn]

With insulate I'd prefer if it were a lower skill point cost with upwards to 30% ice resistance on it, keeping it not triggering ice sheets basically solves frostbite as an issue completely, and having it cure celcius and frozen is a good idea, similar to how Priest functions I'd rather it only grant immunity if it cures those statuses, a solid duration like 3 rounds would be a good starting point for that specific effect.

Not a bad idea is renaming it to Cryotherapy and having it heal a target by consuming ice tiles around it, cure celcius and frozen and grant immunity if cured, then give 30% ice resistance as well.

If its meant to be a support skill, it doesn't have enough utility at the current moment to make it worth a slot really.

[Shujin]

Uh, I like that one!

I always felt like having Ice tiles, as a resource to use would be super cool for Verglas.
And if not heal something like "armor" which is like a secondary health bar that depletes first. Or FP recovery?

[sadbot]

I think a celsius and frozen cure and immunity alone would make it see use, although I think the ideas for bonuses might be a little overtuned. I also think an ice tile consuming heal might be a bit much, verglas kit is already pretty spectacular and rounded and the only thing they don't really have is a baked in heal. Even if they can access healing through meditate and aid anyway, I think those added immunities plus a heal might be a little much unless it was quite a small one, 2 or 3 * ice tiles consumed in 4 range hp or something maybe.

Even so, I think that verglas removing ice tiles is super counter productive to everything about them, mechanically and thematically.

[Shujin]

I disagree about it being not thematic at all. Verglas/people from Hyoya are stronger in a region of snow and ice.
Expand ice is currently the one single thing that even benefits from ice tiles (minus normal Icicle spear having more range). Giving you the option to take away your offensive, a bit by instead using it for defensive is pretty cool and thematic.

The worry about it only curing Celcius/Frozen is once again...Its simply too niche to cost a skillslot/Skill points. I certainly wouldn't get it just for that even on a dodge that is much more terrified of Frozen. I probably rather just 7M guard or something with Ice point guard. For that the rest of the kit is just too good. And the skillpoints/Slots too tight.

[Snake]

Cleanse and Immunity to Frozen and Celsius would both be fine additions to the skill as it is, really.