HP and Fort save, ok, but what do you need BAB for, anyways?
Sure, 4th level Flame Strikes are good, but they are still no match for the vast and totally superior arsenal of the above classes.
There might be an extremely narrow level range, at which druids come out on top (for this kind of stuff, in general they are pretty good, of course

), but that simply isn't the case 90% of the time.
A maximized Flame Strike, for example is no match at all for an empowered Firebrand, unless the targets are completely immune to fire, but then you can still energy substitute it, as you said (tho, not to sonic damage in 3.5), and a character that is going this route is quite likely to have Energy Affinity (the kineticist can do this without even spending a feat, and he only needs a single 2nd level power to totally outmatch the druids Flame Strike at all levels, but they are ridiculously overpowered anyways

).
However, I just wouldn't want to play a druid evoker, as that would reduce the druid to a role he isn't particularily suited to fill.
Flame Strikes are a good way to deal some damage for them, but concentrating fully on that ability, doesn't suit them well, I think.
Bye
Thanee