100% friendly fire here. While the whole tactics thing this time around is limited in so far as you can't setup very specific things, I always ensured my mages didn't use any AoE spells in them and we can still do that. I can also make sure they're mana doesn't drop past a certain point making sure when I pause to use an AoE spell I have the mana required for it so... really that part hasn't changed for me.
I was the kinda person that went pretty crazy with the tactics AI stuff but for most characters it didn't require to much, my main I always just had auto-attack since I played them 99% of the time and only swapped for specific things. The most complex AI behaviors for me where always my rogues. I liked to setup multiple conditions around using stealth to avoid them dying on there own. If they started getting attacked they'd stealth, that kinda thing. The downside in DAO and DA2? Are companions weren't smart enough to position them selves amongst other things.
Now, in DAI, we get control over some of the more important stuff, mana/stamina reserves (mostly important for a mage). We get access to who they target, that is I can ensure they're always targetting my main characters target, or the main tanks target depending on what im playing at the time. For instance my first party, Cassandra, Sera and Vivienne. Sera and Viv will always target my main characters target, and Cassandra will be left up to her own devices. She'll be semi-DMG oriented but be setup to allow for some off tanking if required.
Now though, unlike in the past games, and they've shown this a few times now there AI in general has improved a lot on the base. Where as before the AI was freakishly basic and only functioned outside of auto-attack and range checks if you had the proper behaviors set. That is to say, if I was to use a dagger rogue companion (Sera will be using a bow first time through) they will try to get BEHIND the enemies they're attacking if they can. I wont 'have' to always pause and be like 'ok get behind so you do proper dmg'.. .that's actually one thing less I'll have to pause over on every day encounters unlike the past 2 games. They didn't have behaviors that made them get behind their targets, no try to flank behaviors. So... yeah, I'm not seeing a huge issue with the current setup, even if I wish I could make it so Cassandra would only use Shield Wall when she was being directly attacked and had less then 25% guard. I'll just set Shield Wall to high use and see if she uses it even when not being attacked (I'm hoping shes smart enough not to).