[SixOfSpades]

In order of (my) preference:

Totemic Druid. Spirit Animals are a quite useful summon, since they have many useful immunities, especially in the early game. Sure, Druids have many good Summons available to them anyway, but this frees up more spellslots for other potent spells. The best part about the Totemic Druid is that it has NO drawbacks, since the Bear and Wolf forms were useless even in BG1--they're just even more useless now.

Avenger. The Sword Spider form is at least passably useful, with combat skills far beyond what a plain Druid could muster in the first half of SoA. And the extra flexibility in spellcasting is another healthy boost. The disadvantages to the kit are rather minimal: The CON penalty can be overcome simply by rolling high on CON, and the STR penalty is only important if you're planning to Dual to Fighter, and even then it can still be done.

Pureclassed Druid. Not as good as a Cleric, or a Fighter/Druid, of course, but then a large part of that is due to the fact that there are no really good Druid weapons.

Shapeshifter. First you've got the drawback that all Shapeshifters are the same (since you can't wear armor, and weapon proficiencies & stats become irrelevant in Wolfwere form), and then there's the fact that your paws can be dispelled right out from under you, and even the Greater Wolfwere's combat stats and immunities start to become obsolete once you start getting to the high levels and really good equipment. If you want to play a Druid who can fight, just be a Fighter/Druid.