Pack Size Map: not so much a better chance than more chances. if a monster has a 1% chance to drop an Eternal Item (I made up the 1%) and the Map spawns a Pack of 5, you have 5 chances of 1% each. a Pack Size +100% map would increase that Pack of 5 to 10, so now you have 10 monsters with a 1% chance each to drop an Eternal item.
Cool Down & Storm: Storm lasts 5 seconds, but has a terrible Cool Down of 7 or 8 seconds. you can’t cast multiple Storms like you can with Twister. but lets say you cast Storm, get in trouble and Teleport away, and end up in a Pack of monsters that want to put your head on their locker room wall. if you are in a small area, Storm would be great, but if you still have 3 seconds to go to use it again, good luck. but if it already cooled down, you can cast it again, even if it still has time left on the other casting. you don’t care about the trouble you left behind, you care about the trouble you just jumped into!! there have been lots of times I am glad I had improved CD for Storm, saved lots of Gold not having to revive a lot from dying.