I agree with Geschultz. Archer really does the job. Always stay on the outside of the map, don't mind about the speed boost at the center. Keep your distance at all times. At the end of the wave, keep an easy mob alive to buy the upgrades you need. I bought a lot of golden apples and a few fire resisteant potions after getting the armor. Don't be scared about eating them, when you think you have to, just do it. Make sure you get on top of the cauldrons for the endermen. As for the rest, play it safe. Don't worry about the time limit, just stay relaxed and keep distance. Good luck on your next run!!