Thoughts on chains of ice ...
From a 1v1 stand point I think that chains of ice is balance since the death knight is losing a considerable amount of damage in using it.
From a group pvp standpoint though, I think that chains of ice is incredibly OP, because although the death knight loses damage he can easily incapacitate people and snare people for extreme amounts of time while other players burn them down.
That being said though, I think making COI dispellable is a terrible way of dealing with the problem. It affectively only helps two classes in the game (priest and paladin) while still not helping the 7 other classes. This is thinking about it in a 1v1 view. When in group combat though, priests and paladins can help others and therefore it should be theorhetically more balanced in group pvp. But it is not.
MY biggest objection to making it dispellable though is that the two classes that get the dispel, are also 2 out of 3 classes that get cleanse/abolish disease. So, the two classes that already have counter spells that effectively minimize a DK's damage, as well as completely eliminate a DK's already lack luster burst damage; also get to remove one of a DK's only snare.
In other words, from a group pvp stand point, priest and paladins on a given team can already effectively nueter a DK's damage why should they also be the only classes that can take off the COI.