My computer lags more than most. I almost always crash in sos in the armory and have crashes at other inopportune moments. When in a raid my comp lags enough that there is a couple second delay between when I push a button and it starts to cast. And yes, when raiding I adjust my settings to the lowest possible.
There is something else that I have found that helps me also. If I have my character view in first person and look at the ground I get no lag at all. I can cast away with no lag or problem. Granted this might be useless for a melee class. Maybe this will help someone else who is getting frustrated by lag and is a caster
Additionally, I go on autofollow and do the same thing in sos now and get led through the armory while looking at the ground. No crashes. This isn't the greatest way to play, but till I can get a new comp it helps me.