Not ALL monsters are intelligent and go for the strikers. in fact, my kobolds tend to lob all their javelins right off the bat at the big shiny thing with the big axe....and the dragonshield guys rush them for glory and honor.
Mine run away and get more kobolds. Ya gotta be pretty stupid to attack someone bigger and stronger than you who has a 3 foot length of razor sharp steel in their hand.
DnD however is founded on the fact that opponents are too stupid to be able to gauge the fact that they have no chance to win the fight they're throwing themselves into. You don't think the mountain of corpses needed for the players to get to grind to level 30 were from FAIR fights do you? That would be... heroic.