I am not voting right yet. But I somewhat agree with the OP.
Basically make everything have immmunities, but not inate immunities but rather one skill should be able to justify another skill.
If you have 120 resist, then 26 second immunity is o.k., add it to all the other spells that resist works against and I am happy. Thus if you get cursed and remove that curse with another skill (chiv, mystic) it can have an immunity timer, or force it to be a combination of using a skill to remove it and having the adjacent "shielding" skill (in all cases, magic resist.....unless someone can think of another skill which nullifies the effects of other skills).
The way immunity is now just does not work, first only on 3 spells? Out of how many actually spells? And out of how many Offensive spells? I don't think those spells are/were so powerful to warrant this action, also sleep is nearly identical to Para and yet they do not share this immunity? Not sure how that works out in anyone mind.
I know my description is not the best, and in all likely hood not the best idea for the implementation of Immunities, I am simply putting it out there that I do not mind having them but under the right checks and balances, you should not get an immunity when you can the effect back on before the opposing party even casts another spell, or performs another action.