freeze debuff possible on pinnacle bosses?

I know you cant reduce the action speed of many bosses to zero. However, I wonder if there is anyway to have them count as frozen for the purposes of the cold mastery "enemies take 5% increased damage for every second they have been frozen"?

Yes, you can freeze them.

theres witch masteries that allow all damage to freeze.
youd want a good crit spike of cold damage to get your 1 second
frozen which is hard to get.

more likely your better off with the fastest hitting attack
which will "freeze" but for .1-.2 seconds per hit which wont
trigger the "increased damage for each second frozen by you."
but will mildly slow them overall and allow more hits before
you kite away.

convergence and a lower cast rate/higher damage per cast + frostbite
and penetration is the best chance. I dont enjoy penetration tho,
as most content dies faster to a support gem that increases damage/crit
or cast rate.

Thanks Agnosious for that detailed answer.

How exactly does freezing for .2 seconds not count towards the increased damage for each second frozen mastery? 5x .2 second freezes is 1 second of total time frozen.