The first legit kill I've gotten on an Enderdragon was a week or two ago. On my survival world, I brought into the portal:
A diamond sword with Smite IV and Knockback I (You can imagine how hard that was to get.)
A diamond pickaxe with Unbreaking II
2 stacks of ladders
3 stacks of arrows
4 water buckets
2 mushroom stew
Full diamond armor and a spare set (each set with an enchanted chestplate, but I don't remember what.)
16 potions of swiftness.
It took me 45 minutes to kill it that time. This was in 1.9 Pre-release 6.
One in Survival legit, one with spawned items in Survival and one in creative.
The legit one was killed on half of a single food bar - I forgot to pull my cooked chicken out of my furnace before I went to the End. Diamond sword with Sharpness I, 4 stacks of arrows, Strength I potion and iron armor.
It's pretty easy if you have some okay bow aim and the clarity of mind to NOT LOOK AT THE ENDERMEN. Seriously, the Endermen are harder than the Dragon...