+2 on the iron armor. Iron is cheap and can take a good bit of punishment. Pretty much a must if you got green exploding griefers around. That being said, still don't let them walk up to you and blow their wad. They can deal out a metric fuck-ton of damage point blank. I've had them waste me with full health and 60% iron armor.
Also keep a weapon on hand. I use a diamond sword, kills mobs in 2 hits. If you sprint-punch them it knocks them back quite a bit. Great when you are near lava/cliffs. You can shove them to their death. Iron sword works well too. Bows are nice too, but since the changes to it in 1.8, I wouldn't recommend it for close combat. It's much better in open areas where you can snipe with it.