to clear up blade's post, all the "attack" does is makes it easier for the "damage" to be done. if you are against a high defense opponent, more attack is better than more damage, but against a lower defense target, the damage is better because you have already achieved the amount of attack essentially negate the targets defense, and any more attack will do nothing for you.
the numbers are wrong(as in i am just making them up, but it's the general concept), but it kinda works like this:
att = 2*def -> 110% damage done
att = 1.5*def -> 100% damage done <- "softcap"
att = 1*def -> 75% damage done
att = .75*def -> 50% damage done
very crude representation...don't have the exact values off the top of my head, but that's how it works....i believe it's a log function, but not sure...
there is no real answer to your question except that buffing for attack or damage is relative to the defense of the target. if you have already achieved the "softcap" for attack, then damage is your best friend, and any further attack is wasted(yes it helps a little, but is negligible). on the other hand, if you are not at the softcap yet, then buffing for damage will do less to your output damage than buffing for attack.
as for crit, at lower levels, i find it's not worth worrying about crit unless you can get to at least 30-40% buffed, but if doubling your crit gets you from 2%-4%, then the resources would be better spent in damage or attack
more info about classes, level, weapon, gear level, and intended enemies would help to make a more developed response.