My characters slip on ice outside of battle in Hiberheim. Unless i have the boots or gear to prevent it.
If its your leader only then he or she does not have the boots.
Well, I haven't good explanation of this. Except obvious: all of them goes _after_ leader, so if he falls, they stopped.
But still, I never seen that they fallen. In no case, except in battles. Maybe my luck. Or lack of attention. *shrugs* Well, I can test it, of course... I will tell you, if I'll notice anything.

Moreover, as I noticed, one of my hirelings refuses to go if ice completely blocks the passage, going here only if ordered directly. %) Interesting. Other three characters not demonstrating such abilities, even if one of them is my perceptive leader, and other - intellectual. I wonder, what can be reason of it...
Its really simple. Have boots, run over ice. Have not boots - fall hurt your head, ugh.
Me speak to you in caveman language.
You are mixing here two different things:
1. Ice is the surface that causing slipping and it requires careful walking on it or the special gear. It's the feature, and I am welcoming it.
2. Ice is the terrain that harmful for characters, but still they ignores it, unlike other similarly harmful surfaces. It's the bug.
Problem is in characters behavior, not in ice itself.
Ice cannot kill nor it ever did in the game.
Unfortunately, it eats my time, that I value more than character death. Because I can avoid death, and it's part of my gameplay when I cannot. No "clicking on familiar spot and suddenly died". But I cannot avoid meaningless slipping, not using methods that eats my time too - and it adds nothing to my gameplay.

Note that it's _only_ terrain that treats this way - oil is similar, of course, but oil is harmless for the traveling - even overweight affects movement much more.
Also... try not running over the ice in combat, but walking instead. Step by step.
Yes, that's exactly what I do in battles.

Problem is, I forced to keep the same behavior _outside_ of battles - and that's only irritating for me, as I see no reason for it.