What they did was let you press a single key (eg curse, heal) and then
using internally programmed logic determine who needed to be
healed/cursed, ...
That is exacly what I'm affraid of with Round Robin. The Software remembers which char has already used up a special ability and thereby determines which char that is next. It allows a user to use special abilities in a long sequence without having to remember which char has their ability on CD (cooldown), just by mashing 1 key mindlessly (as soon as the previous duration of the ability from the last char has timed out).

That is a very big difference between this and to actually have 5 different keys and to have to remember yourself who is on CD and who's not at least imho.