TL;DR: it took way more knowledge to become overpowered in DAO compared to DAI. I guess not having to spend attribute points is a big part of that.
It really didn't take that much. It boiled down to:
"Do I have a mage in my party?"
"Yes? Cool, I win."
"No? Well, at least I'll get to use some of these 5000 health potions, then."
There were a couple factors at play. First, there was a ridiculous amount of access to potions, just absurd amounts of potions. The different "levels" of potions didn't share cooldowns, so you could bathe yourself in potions way faster than enemies could deal damage.
Second, mages. Ah, mages. It doesn't take a whole lot of insight to realize "oh hey, if I CC everything and drop AoE on their faces, they will die and I will take no damage." Mage abilities were just way out of proportion with the other classes - which, let's be clear, makes sense lorewise, but did make the combat a bit of a cakewalk if your party contained one or more mages.
Friendly fire was enforced, but FF doesn't even matter if everything dies while they're paralyzed 100 feet away from you. DA:I has the option to turn on FF, and it has much more of an impact (IMO, a positive impact) on the gameplay than it did in Origins.