Spontaneous Divine Caster Druid is the Tier 2 variant.
Ah --
that['s what I was thinking of ... ... but then all the other druid goodies are still on line, so forgive my skepticism about the appropriateness of that ranking. (but let me get back to that in just a minute ...)
even without natural spell, master of many forms allows speaking, which is half the issue.
The other half being somatic components -- which is still a +1 MM feat. + Eschew Materials.
So, a wizard is set up for this by 3rd-5th level -- then just take Arcane Thesis for every spell he plans on using while in polymorph. Done.
Druids don't get to abuse MM the way arcane casters can (or even clerics). Druids don't really have much in the way of 1-round encounter-enders -- their primary schtick is root-dot.
Sure, you can jump through an arbitrary # of hoops with just about any caster and end up as the end-all-be-all awesome-everything. But that's apples-and-oranges -- I'm just talking about base classes at this point (shenanigans gotten through PrC-stacking is a PrC issue, not a base-class issue).