for me personally, and others i'm sure, half the fun of multiboxing has been getting everything set up, tweaking settings and working out/writing and then tweaking useful macro's for my characters.

If you're the type of person that isn't into that kind of thing, you're only going to be getting half the kick out of multiboxing I know many people here get

In terms of macros, there isn't any set-in-stone methods of what works and what doesn't, play around with your macros, if you find something (in this case your assist macro) which you'd like to be more effective in some way, take a look at the many examples already posted in the stickies here have a go at putting bits and pieces into your own macros. It's possible to cram a fair amount into a single macro, especially if you're only dual-boxing (less toon names to use up that precious character-count ) so play around, nick bits of other people's macros (they've shared them here for that very reason!), and refer to wowwiki's macro guide whenever you aren't sure/want to see if something is possible, and most importantly have fun doing so if you can!

As for looting, There isn't any way round this as far as I know but to move your mouse to the characters window and right click. Personally I use free-for all looting, and loot as much as possible on the main character, then second, etc. I do the same with collection quests ( though i try to avoid them), complete the quest on the first char, then second and so on, it makes it easier than using group loot and having to constantly worry about who's turn it is to loot!

And your LOS issues can be solved by simply running that little bit further to make sure your follower is in LOS - that is if I've understood your problem correctly