I consider the Loot-a-rang a large enough quality of life improvement that I don't want to have to do without it. As such, I've turned 170+ characters into engineers. I can only tell you that for me, it's worth it. Whether it's worth it for you, is up to you entirely. Personally, I'm quite happy that post-7.0 I still don't have to bother with targeting corpses and using IWT to loot them, and instead can loot wherever I stand at the press of a button. So the time, effort and materials I poured into getting that sorted, was completely worth it for me.

As for other professions, I've obviously had to make some changes there to accommodate for all those engineers. I run 8 accounts, and tend to play them either in groups of 8 or groups of 4, depending on content - given I almost always play together with other people. To figure out what to do, I made some choices about how many of each profession I wanted, and then established some rules for distributing them among my characters.

I'm someone who likes having characters available to be able to go "Hey, let's throw class/spec x into the mix, see how that goes!" As such, I have very nearly one of each class on each account for each faction (only missing a handful of Hordies). With so many characters available to me, I decided that for each account, I wanted one of every profession. The only exceptions are tailoring and enchanting, for which I wanted two of each per account. This allows me to have profession based teams in ISBoxer, with the aim of making it more manageable and efficient to tackle profession-specific content such as world quests in groups.

Other than that, I made sure that they were distributed in such a way that almost every group of 4 would have an enchanter and a tailor (for looting extra cloth) available. I also made sure all the skinners were of a different class, so if I'd like to go farm with a class team rather than a mixed team, I have a wide range of choice.

Now, I'm not saying I think you should take this as far as I have, but hopefully this gives you some ideas for how you'd like to set things up yourself. Good luck figuring things out and happy boxing!