if tested a lil bit with plague leech, and i think i found a proper solution, or at least a lil improvement
i've already stated how it currently works
i'm doin some tests now for PL when OB procced and no runes avaiable for OB (for Frost 2h), this should raise the dps slightly (from my experience 1-2k dps)
Yeah and for DW Frost it should be about the same logic as Empowered Rune Weapon...when there are no Death or Unholy runes up. Normally I would say when there is no Runic Power to cast Frost Strike, too, but Necro does a pretty good job of saving just enough RP in case of Rime procs.