I get very little loot lag with the social i made for loot all, it's a social via everquest and yes I have mq2 loaded. anyhow- tbh i think it's the input interface or whatever (mouse clicks/movements) my social reads as follows:
/target corpse
/shiftkey /click right target
this works perfect for me. that is if the corpse is within loot range (obviously)
hope that helps
you are making it to difficult all you have to do is
/target corpse
/loot
thats what i use, though you are looting all so i guess yours would work better, the one i do doesnt loot all cause i dont like looting the trash also