For me, this has two points of interest. First, the standard method most of us use to play collapses into one or two tasks (depending on the variety of characters played). For me its controlling the tank manually & spamming a limited amount of buttons for dps/heals (which over time are locked in memory as a routine). For multi-class groups, I would expect it being more complicated at first, but ends up the same way. So I don't see anything really being neglected by this method.

However, my second point of interest is... this explains WHY we may lock up or fail to recover when the crap hits the fan during a run. Especially when beginning multiboxing. When an instance pull goes wrong suddenly we're less competent then a PuG full of 12-year olds. Something that should be possible to live through (with effort) just completely wipes the group because our minds can't always think on the fly for all types of roles (tank / melee dps / caster dps / heals). For me, its usually tank grabs all the mobs while dps preps/launches AES but I don't take stock of healths which quickly neglects the healer's role. Or I heal like mad but the tank isn't producing enough agro then dps / healer go down.

So multiboxing can be multitasking, but it appears to me that once the rhythm is learned it becomes a single task. 22112211221122112211 etc