After thinking it over, limiting these new characters to heroic souls might actually make getting them easier. Other than the fact that it could be a long time before you see them, if you save your fragments you could get dozens of heroic souls or more when they show up. And since there's only 2 five star characters to get, that's like 50/50 chance. Besides, they could actually both be in the same rotation so you'll get either the Baroness or Daedalus if you're lucky to get a 5* pull.
Putting them in Heroic souls separated them from the slew of characters that swim around in normal souls, making them easier to end up getting when you save up lots of heroic fragments. Which I've been earning hundreds of by playing Gauntlet, which is like a billion times less stressful and more entertaining than the arena.
Y'know, usually when I start to dislike something, I usually just stop associating myself with it..... Might be something you should consider, just saying.