To be clear, some macros are kind of important and useful - for instance I make macros like the following:
#showtooltip Shield Slam
/cast Shield Slam
/startattack
for cases when I am low on rage with a warrior and might be turning to a new target - this way I tab to the target, go to hit my shield slam button, but I'm too low on rage or SS is on cooldown... oops... without the macro I'll be standing there not attacking until I either right click or click an auto attack or some other move that I have enough rage for...
I make the same macros for my hunter for when I want to switch targets but may not have focus for the opening shot I want, but don't want to waste focus on something else:
#showtooltip Explosive Shot
/cast Explosive Shot
/startattack
This gets me auto-shooting if I don't have enough focus for the shot I want.
The only thing with these macros is that like all macros, they do have a possible down side - which is the unintended attacking of something you might not want to attack - fortunately this is rare for my warrior, but not so rare for my hunter, so I have to exercise care when switching targets so that I don't target something unintended and pull it by accident.
Back during BC, a castsequence macro was the only way to be effective as a hunter in PvE - but that was because of the (FKN STUPID!) game mechanics. Now, those mechanics are different and due to game lag and such along with the inherent delay to castsequence macros, you can be more effective without a castsequence macro than with one. That said, it takes a decent amount of paying attention and dexterity to manage being more effective than a macro. Not everyone will be willing to practice to the point that they can beat a macro. Some will though.
I remember those huge macros for chain seducing/banishing/fearing focus targets and such with my warlock too - that made a difficult task become "one button simple" so that I could focus on DPSing the pull and not focus on crowd controlling a target - i.e. it made warlock CC as easy as mage CC, which was great.
In short, not "all macros" are "bad". Some macros are extremely useful and IMO necessary for play - like my warrior /startattack macros - these things make my life so much easier and allow me to free up my mouse for movement and my eyes for seeing the screen while my fingers can be a tad less precise on the buttons and still achieve excellent results. A good warrior tank needs to be able to respond dynamically with movement and target selection to situations that DPS and healers don't necessarily have to worry about.
I remember during BC when I was really paying attention to hunters all around and everyone wanted to make one button "do it all" macros that would send their pets, start attacking, mark the target, skin the last kill, retarget mob the pet is on, misdirect the pet, and whisper their cyb0r partner: "what are you wearing" all at the same time. Invariably these hunters got into trouble when they failed to learn all the various little things you do differently in a party than when soloing. I.e. "you whisper to Sumdumhunter: Can you mark my target please?" Next thing you know, the hunter marks target, starts shooting it, their pet charges into it, the whole group is pulled and I get a whisper in response "Sumdumhunter says: What are you wearing?"...
So yeah... use of macros by someone cogent and able to understand what all is going on is great and they can surely smooth out game play. They can even help with gameplay performance for sub average players and for when there may be latency issues which make an otherwise good player appear sub-average. However, all other things being equal in the current game, for hunter DPS, castsequence macros can be beaten by folks who have low latency, good reflexes, a good action bar setup, and who have practiced their rotation.
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If ignorance were painful, half the posters here would be on morphine drips.
Everyone playing WoW knows everything about playing two classes: 1) their own and 2) Hunters