Druids aren't the best blaster class. But for a blaster druid who spams call lightning or might spam flame strike, then perhaps the empower rods could be more valuable than the extend rod.
Compared to sorcerers they get far fewer spells per day, and compared to wizards their blaster spell selection is downright pathetic.
But if you are going to play one, then some of that gold you are targeting for metamagic rods might be better served to purchase pearls of power so you can recharge your spells between encounters.