Dire creatures are to heroic story games what heroes are to heroic story games - larger than life. You didn't just fight a rat, you fought a DIRE RAT - still only has 5 hit points.
Take a moment and compare what you do in your game to the real world. When was the last time you saw any non-domesticated creature with more than 1-2-3-4 hit points, outside of a zoo or on TV? When was the last time you saw something that viewed you as a potential meal? Would you really want to get close enough to poke it with a sword?
Javelinas running wild (they even look a little like dire rats). As such, I've been deer, squirrel, rabbit, duck, and quail hunting - maybe a deer has more than 4 HP... I have seen bear, coyote, wolf, wild boar and wildcat tracks all around areas where we regularly camp - yes, you can drive there, but you need a 4-wheel drive. What I have never seen is a Dire Bear, Dire Wolf or Dire Boar - which I'm grateful for, though I'll take my .30-06 rifle over a sword/shield any day.
So think about this the next time you decide to put a dire animal in a game - it is the heroic adventurer of that species. Try not to let it be just a *filler* fight or useless random encounter that doesn't get across the importance of the fact that at 1st-level, a dire rat isn't just a big rat, it's a DIRE RAT (the heroic 1st level Fighter of the rat kingdom) - that still only has 5 hit points (more than the party wizard).