I don't think it's so much a matter of harshness, it just kinda stretches the life out of the string and many of the newer strings just seem to perform better at lower tensions.
I agree that BBAce at high tension would be better than say, Duralast16 @55.
Let us not forget that the OP is used to high tension Kevlar. (ouch).
Neos 1000, Eagnas Combo 810