The adds only come once every 45 seconds or so. With a single tank, you can burn your AoE taunt every time and get them both.
This is true in most cases and to add to that even if the tank has somehow used up his aoe taunt, all he really need to do is single taunt the one add that is going for the button clicker so it does not get to interrupt him.
The other add will most likely go for the person standing in the middle and that add can be stunned, slowed, pushed or pulled away by both
the tank and
the person standing in the middle until either it dies or the tank's taunt comes out of cooldown again.
There is no reason not to have tanks to do the clicking.