After trying three different class 10 MicroSD cards (and by those I mean real Class 10 cards with 15 mb/s write and 18 mb/s read) formatted by Panasonic tool, I still have lag in clean mode; needless to say that AP patched ROM in Patch mode works perfectly.
My conclusion is: DSTWO cards themselves may differ, thus giving problems to some people and working with no problem for others. It's basically a lottery of whether you get faulty card or not. Since most people, myself included, buy DSTWO for its patch engine (RTS and cheats feature), and this particular game behaves well in patch mode with AP-fixed ROM, I see no reason to bother any more.