I feel there could be a better design than 'make sure this buff is always up or else you are gimping yourself'. That's pretty boring gameplay. I'd prefer to bake the buff into the classes damage and introduce a new ability that has a more noticeable impact on your play. I mean what if savage roar was actually a modifier to other druid abilities that were situational? Instead of flat damage increase, maybe it makes your next healing touch heal for twice as much, or your next shred a guaranteed crit, or your next rake tick like your haste is doubled, etc. It would actually be a button that changed your play and had different uses in different situations.

Just give it a moderate cooldown like 30s-1min and then it becomes a choice. If you have to use it on an oh crap HT, you won't be able to use it for burst on the add that spawns. In PvP it can be used to save your life or burst a focus. So many things can be done beyond push a button, increase your damage.