While I don't have any actual numbers to throw at you, I can tell you that agility raises rogue DPS as well as evade rate, crit rate, and all of those other things you know about. So if I were to equip an item with 10 agility instead of 10 strength, I would not only get the benefits of the higher crit/evade rate, but my list DPS would be raised just as if (or possibly more than, I don't recall exactly) it were strength. Strength also raises DPS, but if you have a choice between strength and agility, agility always wins.
As for the effect of starting stats, I can't say you'll notice much of a difference as a night elf rogue when compared to my human rogue, assuming equal levels and gear. Night elves start with 5 more agility and 3 less strength than a human, as I understand. Your race has no effect on how much of a stat you gain when you level up, so even at level 60, if you have identical gear, the difference will still only be 5 and 3. This makes little to no difference, really, and shouldn't be a major concern when choosing a race. The best things to consider are racial traits and, most importantly in my opinion, whether you like the way the race looks or not.
[Edited to remove stray comma.]
As for the effect of starting stats, I can't say you'll notice much of a difference as a night elf rogue when compared to my human rogue, assuming equal levels and gear. Night elves start with 5 more agility and 3 less strength than a human, as I understand. Your race has no effect on how much of a stat you gain when you level up, so even at level 60, if you have identical gear, the difference will still only be 5 and 3. This makes little to no difference, really, and shouldn't be a major concern when choosing a race. The best things to consider are racial traits and, most importantly in my opinion, whether you like the way the race looks or not.
[Edited to remove stray comma.]