I used to be a guild leader in a semi hardcore guild. We had a few people in the guild who where not up to the same level as our top dps. I took them and the top dps aside and asked the top dps to make a macro which best matched their cast rotations and put it in a cast sequence. Spec's werent debateable in that guild so it was either the low dps wasnt pushing the right spells at the right time, where clicking or had a bad pc (low fps).

The macros where given to the low dps people and told to be bound to key 1 on the keyboard. Then the macro was to be spammed 8+times per second for the whole fight. The top dps people where also using the macro to dps. When we tried it on a boss fight we no longer had any low dpsers. They all came out about the same. This was slightly lower than it would be if people where pressing the buttons manually, but it got over the block in the minds of the low dps people that it was all about gear/having no life.

After the low dps people saw how the macro worked they then (with help from the high dpsers). Learned to press the buttons manually and most of them did improve their dps then quite dramatically. There where still a couple of people whos dps was lacking but I do think it was because of pc/connection issues there.

I do think for the most part though that the problem is with those low dps people, they are just happy to accept that player X is better/has no life/better gear etc. Rather than do the research to maximise their own dps.

Ive done some pug raids with my ele shamans in Wotlk and I just used the same macro as I use while boxing for my dps. Thats because I was learning tactics and didnt want to make any mistakes (Im usually a min/max whore). My dps was always in the top 5 for 25 man raids. Couple of times I was first (Vs far better geared players).

So in summary I dont think Ill ever understand how some people are so bad at this game, but there is hope of improving people if you can get them to follow simple instructions. If you cant get them to do that then you definately need to consider wether you and the rest of your raid group are going to be happy carrying said people for the rest of your raiding days.