Problem with items cooldowns

I need to add a cooldown to single items. For example if you try to use 2 rods of necromancy i would like they have 2 different cooldowns and not a shared one.

I tried removing completely the cooldown group but all items witouth it have a shared cooldown too.
Adding ignore cooldown removes completely it and that is not a good idea.

I don't believe that there's a solution, then, unless you want to make separate items that do the same thing. It's either all or nothing, really, otherwise.

Make multiple items, with different cooldown groups, and then use triggers to change it if they have 2 of the same.

Sigh... before cooldown groups the thing worked good... Damn blizzard!
I decided to use custom value on items and restore the value after cooldown time.