I don't think we can judge if they are weaker then they once were at all. Dominate Wraiths on dominate hives aren't the beings we see die. It seems to me that the less ancient and therefore less powerful hives seem to suffer from in-fighting and well as food distribution issues and they are the ones we really see. To us and to the humans of Pegasus, Wraiths appear weaker as their forces are faced with more then just the "normal" Culling runs that Pegasus is used to. But because we don't know much about hive workings or the Wraiths' culture, we cannot judge that.
All we know is that at the end of the series random Drone deaths and lower ranking Officers are more easily killed by SGA. Michael and the Hybrids don't count as they are no longer feeding so we cannot judge the Wraith by them. Take Todd, we don't know how many shots it will take to finish him off (and to TPTB I never want to find out). At this point, I don't believe that we can never know if the Wraith are weaker then before.