I recognize the sort of importance or desire to 'lead' or 'suggest' through an N/PC played well, and think that there are pitfalls to it.
After all, you're already supposed to be doing EVERYTHING, where the sin are you going to find the time and energy to fight your self? But, I concede that part of the fun is being part of the group that takes down a big baddie.
I would suggest, to those who are considering such to try to keep the micro-management down. Along the lines of KISS, keep it short and simple. Give your character signature and simple at-will powers -- select encounter powers that don't need a lot of book-keeping -- pick daily powers that are clearly either 'the big bomb' or make it part of the N/PC's character that they picked a 'mediocre' power. Try to avoid having too many 'interrupt' and 'reaction' abilities; pre-calculate opportunity attack bonuses, since (at least once) your character is likely to be working with the group to make it hard for enemies to move around. Don't use difficult maneuvers like marking which require extra maintenance. Keep the selection of feats and powers simple, focusing on the basics: attacking, or having a good defense. If there's role-play to be involved, make sure the skills are diverse enough (or in-character enough) to fit a skill challenge.
But, most of all, MAKE IT EASY TO DO. You should be blasting off an at-will power, then preparing an encounter power, and maybe dropping your daily. You'll move around the field, or just strike on one target. Remember, NO FUNNY STUFF. At least, not for combat, which is already enough effort.
After all, you're already supposed to be doing EVERYTHING, where the sin are you going to find the time and energy to fight your self? But, I concede that part of the fun is being part of the group that takes down a big baddie.
I would suggest, to those who are considering such to try to keep the micro-management down. Along the lines of KISS, keep it short and simple. Give your character signature and simple at-will powers -- select encounter powers that don't need a lot of book-keeping -- pick daily powers that are clearly either 'the big bomb' or make it part of the N/PC's character that they picked a 'mediocre' power. Try to avoid having too many 'interrupt' and 'reaction' abilities; pre-calculate opportunity attack bonuses, since (at least once) your character is likely to be working with the group to make it hard for enemies to move around. Don't use difficult maneuvers like marking which require extra maintenance. Keep the selection of feats and powers simple, focusing on the basics: attacking, or having a good defense. If there's role-play to be involved, make sure the skills are diverse enough (or in-character enough) to fit a skill challenge.
But, most of all, MAKE IT EASY TO DO. You should be blasting off an at-will power, then preparing an encounter power, and maybe dropping your daily. You'll move around the field, or just strike on one target. Remember, NO FUNNY STUFF. At least, not for combat, which is already enough effort.