counters
Lord Zardoz, I like your suggestion of a potion of invisibility as a counter. Of course this only works against a caster who doesn't have See Invisibility up, or Invisibility Purge.
I think, though, that you've missed something in this discussion, which is the power of the readied action combined with the silence spell.
You mention the caster avoiding the effects by moving out of the silenced area before casting, right? The thing is, this is impossible if the person casting Silence employs the right strategy..that of readying an action to cast silence when the opposing spellcaster begins to cast a spell.
IE, the sequence is this:
silence caster wins initiative, or survives the opposing spellcaster's first action
silence caster readies an action to cast silence on the ground at the feet of the opposing spellcaster when he begins to cast a spell.
opposing spellcaster begins to cast a spell, which is ruined, unless he has silent spell
silence caster re-readies the same identical action
ad infinitum
With this strategy, a 6th level beguiler can shut down a lich, assuming that the lich doesn't have silent spell. OK, the lich can probably beat the beguiler in melee, but forcing a lich to engage in melee is still a huge tactical win.
Do you disagree? What am I missing?
Ken