Well, that character just died. It wasn't his constitution that doomed him, as much as the fact that I ran out of potions of dimension door, and I just realized I forgot to tumble.

The build I'm using at the moment is:
Drow Rogue
STR 12(11)
DEX 18(20)
CON 14
INT 18(20)
WIS 13
CHA 3(5)
LUC 8
I have appraise, decipher script, handle device, hide in shadows, listen, lockpicking, move silently, searching, tumble, knowledge(magic), and use magic as skills. I get sneaky and light sleeper at level 1, and pick up weapon finesse at level 3. I suppose I'd get two weapon style once I get to level 6, but I haven't gotten that far yet.
I'm not sold on the usefulness of use magic, every time I've tried to use a wand in combat all of the enemies get a pile of free hits on me.
One problem I have is how long it takes to switch from ranged to melee weapons, if I'm sniping at something with my bow, and it gets within melee range, I can't switch to my melee weapon without them hitting me several times. So I just have to chug a potion of dimension door, and I'm always running out of those things.
It seems like once something has caught me in melee, and I don't have much hope of defeating it, my only option is dimension door.
Does anyone have any advice about that, or about the rest of my build?
Maybe I need to train alchemy to get more of those potions...