So we can only add the better buff from a weapon to our level'd weapon, but we can't raise the % of the buff with a lower to get a better stat? So duplicates are still worth nothing, if you got a better allready, but it is just 1% better then the second, you still are unllucky cuz both are 22 and 23. And if you see your next one, with the same weapon and it has lower %, you still can't skip it.
Conclusion for the Valence Transfer; hunting or farming a lich, doesn't help us at all, if we still get unlucky through RNG.
If your plan is, to not make the same mistake with the Lich's as you did with the riven, the trading a Lich Hunt with high % on a special weapon will be very expensive. Instead, just lets add the % from weapon B to weapon A, so all people can get the max out of them. And the huntig missions will not be so explosive expensiv like the riven mods.