I've played a druid to 12th level so far. Up until the presence of 6th level spells, she was notable more for 'spell staying power' than for total damage in a single hit. e.g. call lightning and its bigger brother let you get decent mileage out of a spell for most of a melee (especially if you can summon a few air elementals to give you whirlwinds and up the power). A lesser empower metamagic rod helps out there too. (at lower levels produce flame gives you an attack for 1r/level, then flaming sphere for 1r/level etc.)
Once I reached 6th level spells and was able to unleash the unholy power which is fire seed holly berries though... unbuffed that is 8d8+96 damage, which is pretty bad news.
That leads to the second point - the druid damage spells work very well alongside spell buffing magic items (and divine is best). My bead of Karma lets me cast as a 16th level caster for 10 mins per day so the holly berries do 8d8+128 (avg 164 damage). On one occasion we were assaulting a known trollish stronghold with dozens of trolls, so I used the old incense of meditation (maximise all spells!!) Call Lightning storm did 50pts per bolt, karma-ised flame strikes did 90 damage each, etc. The party sprung for another block of incense from party funds for the next occasion when it became necessary!
(funny that arcane casters just don't have the spell buffing ability like the divine casters though - where are the caster level enhancements or automatic maximising of spells for arcane casters, eh?)