no position issues.?? what... seriously you lose los and then your cast is cancelled, stand to close you have to move for aoe's or die. you have to know where to stand and which direction to face and pay attention to the tank and where he/she is pulling to otherwise you'll be in the wrong place and unable to cast.
no mp issues, tell that to all the blm's who screw up the rotations and have no mana left casting bliz 1 after 3 secs, to get enough mana to bliz 3, with probs a 6-9 sec delay in attacking... which by the way can be deadly in speed runs.
also as blm you need to know when to aoe when not to, manage hate cus blm are massive hate gainers especially in aoe. what to do when you do pull hate.. and no that doesn't mean run to the tank and stop dps'ing.
to op..
truth be told the way most dungeons are run nowadays you cant really afk dps and not be noticed. not that anyone can really do anything about it mind. some dps classes seem easier than others at the average level of play, which by the way sounds like where you'd want to be. take your role seriously but don't expect to be carried through stuff.
and as for mechanics, sorry to say you have to deal with more as dps I would say than tanking.. especially in places like ct and coil.. but even some dungeons have dps specific mechanics that can and cannot be ignored depending on how good the dps is.
if you want to take a break from tanking, by all means pick up a dps class or heals class and try it out but don't expect it to be so much simpler that you don't have to do much.