I played an epic druid for a short while... I have never played such a powerhouse combat monster before or since, and I say this as a person who has built a character for the express purpose of breaking the dragon disciple wide open. Here are some key points for when you top 20th:
1) Your first three epic feats should be gargantuan wildshape, colossal wildshape, and improved elemental wildshape. You can now wildshape into primal elementals (cr 35) starting at about 24th level. You gain like +48 natural armor, big SR, DR, nice feats, all sorts of cool stuff. Fringe benefit: You can also wildshape into the various elemental weirds and fill the party in on the entire adventure before it happens.
2) The single monk level adds a nice AC boost, but where it really comes down is epic buff spells. These will increase your combat capability in primal elemental form beyond all rational expectations for your level. You can get decent AC and SR boosts, and a little reverse engineering makes it fairly easy to deduce a greater magic fang seed to give +15 or so to your natural weapons/attacks. Those can easily be made permanent with the 100-day casting time option, leaving your daily allotment for ability score boosters (since your items won't function while wildshaped).
3) Don't underestimate A Thousand Faces (alter self at will). Take the Hover feat (MM2), and even your primal earth elemental form is now air combat capable.
4) Improved spell capacity, persistant spell. You're no cleric... but with MotW, you can turn your animal companions into some mean fighting machines. You haven't lived until you've seen a pair of legendary bears with persistant animal growth, nature's favor, nature's avatar, regenerate critical wounds, and uber magic fang (epic spell of fairly obvious purpose) in action.
5) If your DM is feeling generous, you may be able to con him into allowing the OA "shapeshifter's" armor enchantment to be applied to other items, allowing the bonuses to continue to function while wildshaped. It's a reasonable request - at roughly equal cost to a wilding clasp, it can't be moved from item to item. It's really just icing on the cake though, and the four points above are all above the table and perfectly sufficient to turn you into an absolute combat monster.
Hope that helps.
--Impeesa--