I think you are dealing with two issues. One is the threat of the sanctions to make bad actors in the previous government stop doing the wrong things: stop killing people on the streets and stop the violations of human rights. For that intention, they have served their purpose.
The other reason you would put into place economic sanctions is to be able to subsequently recover the plundered assets. There was an article today by Andreas Umland stating that the Yanukovych family alone probably would be a potential source of recovery to the tune of $12 billion in assets. So, from our point of view, this is not the time to stop the economic sanctions. To the extent that those assets can be frozen and then be retrieved and returned to the Ukrainian people, it is absolutely necessary that it happen, given their current financial situation.