Correct me if I'm wrong, but in addition to lead, doesn't running water prevent some divinations? In response to a divination-heavy enemy, one of my players constructed an "Honesty Room" with a very tiny moat around the edge of it.
Minions are good, and so are possession and charm spells. If you're an evil mastermind and there's an old noble you want dead, there's nothing quite as fun as:
1) Locating a young man courting an attractive young lady.
2) Having a minion use Change Self to appear to be the old noble, and have him make an insulting remark about the young lady in a public place while the actual old noble is otherwise occupied.
3) Drugging the drinks of the young man and his friends with a slow-acting poison that causes temporary Wisdom damage.
4) Having a different minion use Alter Self to appear to be the young lady, and have her come weeping to the young man, crying that after the insulting remark, the old noble sought her out in private and made unwelcome advance.
5) Casting Modify Memory on the young man's friend and have him "remember" seeing the old noble do what the fake young lady said -- with a leering smile and lecherous eyes.
6) Casting Charm Person on the young man and, as a trustworthy new acquaintance, advising him that "this sort of thing has happened before, a shame no one is bold enough to face him, I've got the key to his private chambers if anyone DID want to try and stop him before he ruins another young lady..."
7) Sitting back and shaking your head with a horrified expression when a young man, mad with jealousy, kills an old noble who nobody could ever believe would do such a thing. Young people these days, violent and hotheaded. Why, even the young lady herself denies that the old noble ever so much as talked to her. What that madman was thinking, we'll never know, although thank goodness even the divinations confirmed that he did indeed kill that poor old noble...