The problem is that in order to get a hashrate comparable to that achieved with the 1.5t3 version, I have to use both --oc1/oc2 and --mode options, at least on 1070s. --ocX alone gives inferior results; so I have to wait till it finishes and finds kinda the best mode, and then add that mode to the command line with either --oc1 or --oc2 (depending on the power limit and thermal conditions for particular cards). Not sure if that procedure gives the best possible result, but it's definitely better than just running --ocX.

Imagine my frustration: after spending a lot of time and efforts I get the same hashrate that I got with the older version literally within a minute, just by empirically selecting an appropriate kernel.