Currently in s1 so my comments are only from my exp in s1...
I am actually not too sure on where I stand on your suggestion.
There's a part of me that would agree/like to see. Eg. better pve lightning tank, more access to supports for atk penalties, heal prohibition to rares, epics. Ice has like pargu (rng atk pen2) and gulai which is very limited)... Rad/lightning has like only 1-2 heroes that applies heal prohibition and yet pillar boss heals like crazy.
But there's a part of me that disagrees with your suggestion. This is because in some ways, it is more fun to make lineups with these weakness works.
Eg.i spent lots of time finding out how to use thia, zharloth, gladros to make the team last for full 8mins in resurgent dragon. Also making Megan, ice shield to let whole team last 8min was a surprise. In these eg, I do not have a conventional tank. I used to think voresh was not good enough to be solo healer but I was wrong here...
What I am trying to say is, these weaknesses in affinity forces us to think of creative solutions.
If every affinity has a full variety of what other affinities have. Then it's just a template of choose obvious tank, obvious heal, obvious debuff, DPS in every team.