sunny,
you did some modifications on the ho thresholds, which is good to shift MS in dedicated mode, but you should also perform changes in order to shift MS in idle mode !
To do that, you can try to put a cell reselect offset = 10dB in 1900 cells, and Cell reselect offset = 0dB in 850 cells.
if you look at some post one month ago, an expert in ericsson have done a full explanation on the ericsson’s HCS management.
regards,
pix