I've re-read the spells, and it looks like you are correct.
This tactic requires coordination from two casters (I hope OID isn't a cleric domain spell), and OID is very powerful (8th-level). Let's also not forget that Harm, as written, is broken!
Your only hope is to avoid a touch attack (eg with Displacement, Mirror Image if you're a mage, etc), but if your opponent wizard has a bat familiar and a Darkness (or Darklight FRCS) spell, then you're a real goner.
Does a Ring of Freedom of Movement help? Certainly a Protection from Evil spell (since OID is a compulsion, and PfE is only 1st-level).