The general consensus is that Allomantic power is significantly weaker in the new era, since the noble and skaa bloodlines mixed. However, many skaa were mistings, since Preservation was able to Snap them with the mists. This means they had enough noble blood to constitute mistings- and that, according to the theory that power dilutes, would be unlikely if they were only distantly related to a single noble. Furthermore, the 300 years would mean that mistings were significantly weaker during Wax's time, but nothing indicates that. Soothing, Coinshooting... its all still powerful. We also know Alendi was a seeker, but a very weak one. Perhaps Lerasium makes its initial user very strong, but any power passed on is at a set level? In addition, power passes on more frequently than we think, if a large amount of skaa were mistings.