That's because you're not invisable. You're just...insignifgant to the eyes of most people, ie their gaze just slips right by you
Correct.
Don't you mean 1 turn +1 turn/3 levels? otherwise that would be extremely potent
Actually, the current duration (1 Turn + 1round/3 levels) seems enough according to my tests. 60-90 seconds in the game means a LONG time, many battles last only 10 rounds or less. And if I'd greatly increase the duration of this ability (which would be reasonable indeed from a logical point, I agree here Jinnai), it wouldn't force players to sacrifice additional points on this HLA

. If you want a really long insignificant state, then simply pick this ability at least twice, and re-activate it before the duration expires.
Like i said though, this should be dispurtable like a mage casting a spell if its possible.
You mean the insignificant state? It ends as soon as the monk makes an action that is considered "non-defensive". I'm not ure which spells or effects remove the sanctuary effect though - Dispel Magic and True Sight maybe.
No more powerful than wizard's foresight, Maestro (that's the HLA master, I think).
Heh, you could have a discussion about this with Caedwyr - he told me many-many times he finds Foresight one of the less useful HLAs ever...