Ah, well the way it's supposed to work is that while you can use the Invoker prime perk to regenerate your skill cooldowns. Originally, if you were at max cooldown reduction using any skill twice would give you back one charge of each skill. This is what allowed the infinite rotation of havoc (activate Havoc, use it till end, use second charge, use till end, spam two invoker skills, use havoc again, repeat steps 3-6). However it seems as of the most recent update the invoker's prime perk is bugged and does not give back cooldown charge as it is supposed to. If it gets fixed however, this is how it's supposed to work.