I don't know about the "corrupted" epic idea but I definitely think the prizes need to be shifted.

# 1 New Epic +
# 2-10 Old Epic+ or New Epic Reg. whichever has better stats
#11-25 Old Epic+ or New Epic Reg, whichever has worse stats.
#26-50 Old Epic
#51-100 Same as current
#101-250 4*+ armor

Right now the difference between top 500 and top 250 is a DP Key and 3 fusion stones..i.e. not enough to care about.
Same thing with top 100 vs top 50. the difference is so very tiny that it really doesn't matter.