VHF/UHF QRP DXing with weak signal digital modes?

When there is a decent contest with some portable stations with decent antennas about, it is surprising how far can be covered with QRP kit on 2m and 70cm. This makes me wonder just what sort of ranges could be covered with QRP and modest antennas on these bands using WSJT digital modes.

Going from SSB to one of the more effective weak signal modes is like gaining another 30dB, i.e. far more that the antenna gain of a big contest station, suggesting that ranges of 200-300km should be ALWAYS possible on 70cms with quite modest QRP stations with small yagis or colinear vertical antennas in flat band conditions.

I am speculating what sort of ranges should be possible under flat conditions (no lifts) with 5W and a small omni or broad beam yagi such as a Moxon or HB9CV.  When I move to the new QTH I think some 70cm skeds are called for with stations out to 300-400km using WSJT modes using 5W or less.