Seriously. An 8/4 for 4 mana is already very good, being in green for easy trample and being outside of lightning bolt range. So a blocking creature and a lightning bolt will do the trick but then the opponent gets another attack phase with all his creatures??
Anzrag will keep the damage from previous combats on the same turn. But there's no incentive to block it one creature at a time. If you can put enough power in front of it to kill it, you should do so immediately. If you can't, you're going to lose all your untapped creatures, and shortly thereafter, the game.
I guess there will be times when you can just take the eight damage (plus whatever other attackers are coming in) and then win on the backswing, but I doubt that'll be the most common scenario.