No, the cloak works for me. I use absolutely no mods, not even fixpacks. Only patches. The only way you can protect you illusion spells from being detected by magical means is through Spell Immunity (Divination), however, thieves can still dispel your illusions through their skill.
“The world breaks every one and afterward many are strong at the broken places. But those that will not break it kills. It kills the very good and the very gentle and the very brave impartially.”
Kuriosan, a famous kensai13/mage14 from the Tactics mod. He's there to show you what you can do at low level though with good items, class and knowledge of defensive spells. He easily wipes whole parties of higher-leveled characters if you're unprepared. ^^
