>>how do you go about healing the whole group... or individuals?

I highly suggest you get something like the X-Keys. What I have is 5 sepereate buttons for the same heal, & 1 corrisponds to 1st party member, 2 to the 2nd, etc... I use "pitbull unit frames" & sort party by name.

>> Also, do most people use /assist focus when targeting mobs...
dont use /assist, use [tartet=focustarget] . This way, on the clone that needs to sheep a particular mob, you just set his normal target to that. He will still atack the other guy (the focus's target) but sheep his main target.
There are people with more macro experiance that have laid this out in the macro forums better than I can.