It is not necessary to perform deskew on a DL850 when using a current probe. The DL850 does have enough resolution to perform deskew and will not be able to find the time offset.
Typically the deskew value ranges from ± 100ns in 0.01 ns steps. This means that for skew levels less than 100ns, the resolution of the skew must be 0.01ns. However, the resolution for the DL850 with the max 100Ms/s module only has 10ns resolution. For the 10Ms/s module the resolution is 100ns. In both modules, there is insufficient resolution to detect the skew.
Please download the file for an explanation of deskew, taken from the DLM2000 instruction manual IM710105-01E.