Well, the closest thing to compare this card to is rage potion, so lets try balancing it with that...
unupped: upped:
Rage Potion: BloodLust: Rage Elixer: Frenzy:
3
4
3
4
+5 atk +6 atk +6 atk +8 atk
-5 HP -1 HP -1 HP -1 HP
In both cases, the potions can not be used to buff fire creatures (unless a lava golem is grown). Your card can be used to buff all fire creatures (except pheonix and golems), and is better than rage potion in all aspects for a mere one more fire quanta. (Note that this isn't very good for CC, a major use of rage potion.) The damaging adjacent creatures is an interesting mechanic, but probably not as powerful because you only need a few creatures in a rush of this type. Overall, nice idea, but maybe raise the cost by 1 (unupped and upped).