When in an instance, which character do you usually drive from?

I've played a Paladin Tank since BC and I can't help but try and drive from my tank because I'm just used to being the MT, but I find that I'll get behind on healing or missing procs, or movement because they're just not in my view or I get distracted.

My group is composed of : Paladin Tank, Frost Mage x 3 and Shaman Healer. I just started multi-boxing in Legion because my friends quit playing but I still wanted to do content (that wasn't LFR) without having to commit to a full time raiding guild.

It's probably just a time/practice thing for me.

I suppose that my goal is to be able to seamlessly switch from between my toons and still have things go off like I expect them to (i.e. tanks still tank/mitigate dmg, DPS still casts their rotation, Healer runs through their rotation).

Thanks for your input. Looking forward to hearing what works for you :)