pierce creates DPS geometrically, (http://en.wikipedia.org/wiki/Geometric_series)
the formula is = damage% / (1 - Not pierce%)
.85/.65 = 130.7% avg dps
I am trying to figure out, would I want spike damage, or consistent pierce?
Gold 46% pierce, .85/.54
= 157.4% dps, more consistent dps
black rune, +24% consecutive damage on pierce
.85 SUM (.85 * .35^x*1.24^x)
= 150.17% avg dps, more spike
it is nice to see a 3 pierce arrow do 162% weapon for a hatred gen skill (3 pierces happens .35^3 = 4% of the time) and for PvP, a nice auto targeting arrow is hard to pass up
but I have a question about the black rune, is it multiplicative 85%*1.24^n, or static 85%+24%n ?
if it is static
SUM .35^x*(.85+(.24*x)) = 150.65% (not much change)
3 pierce arrow does 157% vs the 162%