at first I also had a problem with freezer and some of his guys being stronger than everyone but then I remembered saiyans are a warrior race with an ability getting a (huge) power boost the moment they almost die and having two transformations(giant ape and ssj).
what if freezers race and his minions have similar traits and abilites? that's the only reasonable thing I can think of (sure still a bit BS in my tase but waaay better than gohan not able to lift a rock anymore)
also I still have a problem with freezer being revived after more than a year (yeahyeah, I know dende could have made shenron stronger and stuff but why removing that rule? reviving is still against the nature)