A decay means that out of the laning phase, there has a be a way for her to charge up her stun and still let her use her full combo on someone with her stun up. Otherwise, with her current cooldowns, her stun will never be up until after a teamfight ends. Her current W and E cooldowns are way too long for this to be feasible, but if you lower her E cooldown, she can just spam it in the laning phase to get her stun up much more often due to the small amount of mana it costs. And no, scaling cooldown will not work because maxing your useless shield first is pointless and a huge hit to your damage. You definitely don't want to lower her W cooldown since that means AoE fire up in a teamfight much more often.
There have been speculation about making her Q a skillshot as well, which I'm strongly against because it's just so pointless. There's nothing wrong with her Q. Why are you making it harder for her to land it? Yes, it's a point click stun, but it's what follows up that makes her hurt. The projectile speed of her Q is so slow, even if you manage to walk just a little bit away, minions will be in the way which makes it harder for her to get in range for her W. Out of lane she'll be popping Tibbers for the AoE stun most of the time. Not to mention, this'll make her a mana whore outside the laning phase.
Maybe I'm being a little too pro-don't-nerf-annie because of all the "Nerf Annie!" threads, but really, Annie is not the biggest of our problems in terms of champs with counterplay. She's an immobile, close range, squishy, burst mage. Just pick 1 of the 8 million mobile champs out there and Annie's going to have a hard time against you. (Hell, if you really hate Annie so much, pick Brand and just eat her pre-6 and make sure she can't even get RoA until 20 minutes into the game.)