Blizzard’s philosophy on character customisation has evolved over the years.
In diablo 2, you could nominate 5 stat points each level. Sounds interesting at first, but ulitmately if you chose barbarian it’s likely youll pick strength and vitality.
So in Wow they thought, “with each level up, we’re just going to give you your stats automatically because ultimately the choice isnt meaningful enough. We will keep the talent tree though because that’s cool”
Over time, Wow’s talent tree design was getting a little tired. I believe ghostcrawler made a good post about it. To paraphrase, “Is selecting a talent that grants 1% crit really that awesome?”
Eventually, they landed on the idea of having the player make fewer choices, but more meaningful which is where Hots is today.
In your example, you said it would be cool to modify an AA based hero and give them more spell damage. Whilst that sounds great, can’t customisation options like that be adopted into the current talent tree set up?
For example, at level 16, varian can choose between more armour or more spell power despite being an AA focused hero.
Less decisions; more meaningful