if and when the 3rd legendary slot is opened to us, i think it should only be for utility legendaries
3x dps would be just too much of a damage power spike imho
and having to equip utility legendaries would make them used as well as having a nice balance of damage and utility on your gear.
plus it's much more interesting to select from those than to dps ones
dps legendaries are always "this gives x dps so use this over the rest" utility legendaries are more interesting than that.
obviously they'd need to put some new ones in cos some classes dont have that many but still
what do you think?