Well, I've been playing DAI for about a week (well, 5 days) straight, and I haven't come close to finishing it
But at least I can give some advice towards builds and skills and stuff 
PS: Fantastically glorious game! Dear god, I understand now why it took so long to make.
First up, my team. Purely out of preference, I'm playing with Cassandra, Dorian and Varric. I tried playing with another rogue and mage and my inquisitor as aggro tank, but it didn't work. I don't like drawing aggro, and cassandra is so much better at it anyway. Blackwall would also work, I guess, but Cass is my LI and she has an anamzing focus, as well as templar, which rocks. Also, I'm playing on normal, so this strategy may not apply to harder difficulties, but I'll see what I need to change when it comes to that.
What I figured out pretty early is that the absolute number one most important thing is, is disabling and detonators. Enemies can't hit you if they're knocked down, frozen, feared or asleep. And detonators make for huge damage. Next most important thing: guard. Unless you have 2 mages barriering, it's not constant and you're at risk more than half the time. And even then, it is usually only for half the team members. So even though it's a mage given to have this, I don't find it something to rely on. Guard, now that's where it's at. Lastly, aggro. You NEED someone to draw aggro. If not, enemies go straight for your squishy ones. And they don't have anything to defend themselves properly, or to defend their HP, anyway.
So I came up with the following setup:
My inquisitor. He plays a 2-handed reaver. This is the team's damager. I did a lot of experimenting to try and find a good combat style, and I've finally settled upon one, I think, that is fun and strategically potent.
The skills are: Mighty blow, bull charge, dragon-rage, devour, roll, unbowed, chain and mark of the rift (whaaaat? no ring of pain or madness? No. And me tell you why.)
The idea is this: Bull charge to gain guard and knockdown enemies. Usually I bullcharge to the archers or mages, to take them out first. Cassandra draws aggro for the melee enemies anyway. After a bull charge (with it's mandatory upgrade because that is AWESOME!), you get a free devour. Now, here comes the good part. Devour upgrade ups your crit chance. I have three passives which do something on crit, and that is reduce my cooldown (2H), sunder armor (2H) and weaken enemies (battlemaster). Put an unbowed in here. Since the next up is dragon rage, which should crit a bunch, you **** people up and restore yourself. also, dragon-rage's upgrade cools down devour even more. Next, there are two options, either keep switching devour-dragonrage-devour-dragonrage-etc. Or, if you want, chain with the stomp upgrade into mighty blow, which should do massive damage (when you also have the coup de grace upgrade and mighty blow's upgrade).
Basically, the premise is to reserve as much stamina as possible to continually do devour. Bull charge is excellent for that. And while not using devour, use mighty blow and dragon-rage for damage. Use unbowed as often as possible since it is basically free guard, and it staggers enemies close to you.
No, I don’t use madness. I find mark of the rift strategically more useful. I also don’t use torrent of pain. Why? Because it uses up a slot which I can fill in with more useful abilities. Sure, it adds to your devour and dragon rage, but it sucks up soooo much stamina that your other abilities are neutered. I found myself constantly in stamina shortage. This way, I can just use devour every second it becomes available, and that heals just as good.
For items… Critical chance should be your main focus. Get it anywhere you can. After that, get heal bonuses (for devour, it’s a little bit, but it helps). Lastly, go for maximum health, attack and strength (maybe cunning). I also found a ring off a dragon (such fun boss battles!) I killed which gave me +10% heal for every kill. This basically makes a reaver broken
I found it off greater mistral, iirc.
Cassandra: She is the backbone of the team. She’s there to draw agro, stun, dispel, defend, … She’s glorious.
The skills: shield wall, shield bash, chain, challenge, war cry, dispel (or whatever it’s called in templar), wrath of the heavens and rally.
Rally is just awesome. It provides everybody with glorious guard and stamina. It’s fun to see mages and rogues with guard 
The AI is overall very good with this setup! I’ve actually never once saw her die (well, there was that one time with the 2 red lyrium giants… but that don’t count imo), not even during dragon fights! And she’s ALL up in the dragon, constantly!
Both war cry and challenge, yes. She NEEDS to draw agro. Also, the abilities boost her armor and stamina nicely. Get the taunt damage passive. Heaven’s wrath stuns a lot, which is glorious for combos (and damage, when fighting in demons, which you’ll be doing plenty). The same goes for dispel. The others are self-explanatory.
Dorian: Wall of fire. WalloffireWalloffireWalloffireWalloffireWalloffire. Wall of fire. So friggin awesome.
Skills: Wall of fire (
), Fire mine, winter’s grasp, ice mine, fade step, dispel, barrier, haste.
He’s a demon, plain and simple. The wall just does so much damage, and keeps plenty of enemies off of you (nothing funnier the chaining an enemy back onto a fire mine after they’ve run fleeing for wall of fire XD ). Dispel is used for combos and… dispelling. Ice moves are used for combos. Seriously. Ice rules so much. Very few things are immune to it.
He’s fantastic. Wall of fire.
Varric: He’s a combo monster.
Skills: Full draw, longshot, stealth, sleep powder, poisoned weapons (toxic cloud sucks), throwing knives, leaping shot and hail of arrows.
Basically, just let him stand in the back, put people to sleep and combo with longshot together with dorian and Cassandra. He can do some real damage, this one… Throwing knives are good as well, for sundering armor on bosses, poisoned weapons with the proper upgrades do real nice extra damage. And his focus, because, well. Guess what? Damage.
Well, that’s my team right now. Wouldn’t trade it for any other. I’m loving this game to bits right now 
One thing I do find weird though. I’ve found plenty of amulets of power, but only for teammembers. I’ve found 4 (four!) amulets of power for varric, but like, none for dorian. It’s kind of weird. Also, the only extra point we get for the inquisitor is through the inquisition perk? Nothing else (not that I’ve found)? That’s kind of annoying. Because right now I’m level 21 with the quizzy (20 for the others), and it’s slow leveling… I could use with some more points, bro!