Really?
Druid20 is no more powerful than Cleric/Wizard/Sorcerer20 with Core rules. They get no wild spell
Natural Spell, PHB page 98, is I suspect what you mean.
, I don't think there was any wild armor
Wild Armor Property, DMG page 219
Dragonhide, Special Materials, DMG page 283.
Sure they can transform into an elemental but a Wizard can summon like 10 of equal power.
So can the Druid - Elemetal Swarm, PHB 226.
They outstrip the martials on diversity but a Fighter 20 is still gonna beat the snot out of a wild-shaped druid unless the fighter has a very skewed build. Keep in mind we're talking PHB and DMG only here, no splats, no UA.
Dwarven Druid-20 sets up for the encounter, 2 hours in advance (e.g., daily preparations).
Puts on his +5 Wild Dragonhide Fullplate (took a feat for the proficiency; also takes Power Attack, Quicken Spell, and Natural Spell as feats - that's four of the seven the Druid-20 has - there's still room for Spell Focus(conjuration), Augment Summoning, and one other for flavor or use - Craft Wondrous Item, maybe).
Casts Barkskin (10 minutes/level, will last a little over three hours; PHB). Recasts as needed later on (it's only a 2nd level spell - Druid can have five copies if he wants, and at a little over 3 hours each, that's basically good for all day).
Casts Longstrider (+10 Move - and at an hour/level, lasts all day).
Casts Air Walk (10 minutes/level, will last a little over three hours; 4th level spell, can recast when it wears down, and be good basically all day)
Wildshapes into a Dire Tiger (MM).
Casts Greater Magic Fang (1 hour/level) on each natural weapon (Claw, Claw, Bite, Rake, Rake). Five castings, but it's only a 3rd level spell, and it lasts all day.
This guy has one single magic item on his list. There could be lots more, no problem. Even with the Wildshape errata, nothing stops him from taking things off before Wildshaping and putting things back on after Wildshaping.
Assuming the elete array (15/14/13/12/10/8), with stat priority: Wis, Con, Str, Int, Dex, Cha (all level boosts into Wisdom), before Wildshape, he's got: Str 13, Dex 10, Con 16, Int-10, Wis-20, Cha-6.
After his suite of buff spells, he's a pumped up Dire Tiger:
HP: 20d8+60 (average of 150; 153.5 with max first HD).
AC: 35 (-1 size, +2 Dex, +11 natural, +13 Armor)
BAB: +15
Attack: Claw +27 Melee (2d4+13)
Full Attack: Claw +27 Melee (2d4+13), Claw +27 Melee (2d4+13), Bite: +22 Melee (1d8+9)
Pounce Attack: Claw +29 Melee (2d4+13), Claw +29 Melee (2d4+13), Bite: +24 Melee (1d8+9), Rake +24 (2d4+9), Rake +24 (2d4+9).
Move: 50 ft.
Oh yeah - and with Quicken spell, he can put out a few Cure Critical Wounds in the middle of combat without slowing down, and keep a Bull's Strength or Bear's Endurance spells handy for the first round (increasing both to-hit and damage for each attack, or Hit Points).
Additionally, he's got an Animal Companion to act as a flanking buddy (flanking is in the description of some of the animals on the list, so this isn't a problem for the Druid to arrange).
Further, the Druid can also cast a few Save-or-lose spells.
Moreover, all of his buff spells included in the stat-block above can be maintained basically all day (nothing less than 10 minutes/level, and they're all low-level enough that he can prepare enough copies to go 15 or 16 hours), and as he's preparing multiple copies of each anyway, he can re-cast them if dispelled.
How strong of a fighter can you build, using just the PHB, DMG, and 3.5 MM, on the elite array? Druids get even worse on a point-buy, because there's really just two statistics they need - Wisdom and Constitution. And they can get away with a mediocre score in either.
Then again, the Druid could just cast Shapechange and be, oh, a buffed-up Planetar all day. Or maybe a Choker (casting two spells per round). Or a Nymph (best used if the Druid did not dump charisma, as done in my example above). Or whatever.
Druids and clerics are really good at buffing, obviously, but I think it is erroneous to assume they are always fully buffed and operating at peak efficiency.
At 20th, they can be (barring a DM who routinely uses Dispel Magic - but then, the build above is using multiple copies of all buff spells anyway, and a Druid can make use of a Bead of Karma (also in the DMG) to make things tougher to dispel). Plus, you know, a Fighter-20 can't cast Greater Dispel Magic or Disjunction very easily.
A martial character on the other hand really only needs to worry about where his HP are at since he's either 100% effective or on the ground, bleeding out.
... that is, of course, assuming he hasn't been blinded by a Sunbeam, turned into a cute little bunny rabbit by Baelful Polymorph, Entangled, held up as a target by a Summoned Elder Air Elemental, or any of the other nasty things a Druid can do.
Your experiences probably vary from this, simply by the nature of your original statement, but I rarely find that buffed up spell-casters are as big a threat as some say. Dispel magic is easy to cast
Yes, but not by a Fighter - and a prepared Druid will be able to rebuild his buffs after the fight's over. Meanwhile, the opposing spellcaster that cast the Greater Dispel Magic (or Disjunction) spent an action focusing on just the Druid - and D&D is a game designed for a party of four. That's one round of lose for the opposing caster. And while it weakens the Druid it's spent on, it doesn't get rid of the Druid's actions - so the Druid can simply return fire with something else. Maybe a readied action to disrupt spellcasting with a Flame Strike, to keep the opposing spellcaster shut down after he so generously wasted his first turn.
, forcing concentration checks is easy to do. Trips, grapples, blindness, silence. Not effective all the time (suck it, divine favor) but definitely where the advantages lay when beating up spell-casters.
A proper Druid-zilla does around 90% of his casting out of battle, where concentration checks, Silence Effects, Trips, Grapples, Silence, and (normally) Blindness don't apply.
Anyway, just my opinion, everybody plays a different game.
Now, granted, the Druid-zilla build above doesn't really start taking off until higher level, but even reasonably early on, he's no pushover.