I've found that leech with necrotic is pretty decent, because you can just save a rime proc, clear your runes, use leech, then the free howling blast puts necrotic back up.
agree with everything except plague leech. feels too clunky and is really slow when you need it. would rather play with plaguebearer
And its also easier for removing diseases so targets can be cc'd, doesn't have the problem of needing both diseases on to remove.