/disagree with loki
i'm raiding dest. 0/21/40 (shadow). I've also done the 17/0/44 + other variations. +hit is the most important factor. unlike afliction locks, we have no talents for hit. we also use more destruction spells so resists are a big issue. both on trash and bosses.
for trash aim for 5-6% +hit. this is easily doable (around 74 +hit) for bosses just get as much as you can without loosing out on the other stats to much.
after hit, IMO the next most important factor is getting 20% crit rate (25% including devestation). this is the 'sweet spot' for destruction crit rates as in theory you'll be keeping imp.SB proc up near constantly.
after all this, +damage is then what you need to focus on while trying to keep your other stats the same / increasing. also unlike afliction. your hp and mana are also very important. running around with 25% crit, 1000 +damage, 200 +hit and 4k hp and mana isn't worth while at all, try to get at least 8k mana as destruction is the most mana inefficient dps we have.
the choice of +damage over +shadow or +fire is also important as in the end, anything up to 30% of your damage will be done by the other spell school, IMO the best gear set you can get pre-T4 is the mana-etched due to the 2set bonus, (the 4set being good too, but the 2set is the best part). the decent crit rate, +damage and decent balance of stats. if you were to go for any crafted items. the girdle of ruination is worth while (waist) and the spellstrike set + mana-etched = great hit, crit, damage with mediocure stats.
POST EDIT
don't ever get mana/5. you're a warlock so LIFETAP. we don't need mana/5. it's a wasted stat for us and no offence but any warlock with it deserves a guild kick.
Edited, Aug 17th 2007 7:17:18am by Jenovaomega