I like drama. A game shouldn't have basically only that though.
My problem isn't about the war between mages and templars. It's with the fact that you sided with one faction, which leader eventually betrayes you for being crazy. That's not good drama, in my opinion.
Yeah I see what you mean, like if you sided with the mages, why does Orsino still go crazy?
But at the same time, Orsino was already dabbling in blood magic and prepared to go crazy. And if you sided with the templars, Meredith was already dabbling in the red lyrium and about to go crazy. The blood magic existed before you made the choice and the red lyrium was already in play before you made the choice.
It also means that essentially both sides are right about each other. And that's what validates the heated opinions of everyone in the game. No one is right or wrong all the way. Fenris is right, and Anders is also right.
So I mean, yeah, if you sided with the mages, perhaps Orsino could've just not turned into a harvester - he could've just not gone through with his ritual. But then if you did that, how would you just as effectively bring home the idea that Orsino and the mages still had blood magic up their sleeve all that time anyway? That, even though you sided with the mages, the side you sided with was wrong? Would Orsino confess it, and you find incriminating letters between him and that blood magic murderer, and then decide how to react to the discovery, without the boss battle happening?
If this route were taken, the flip would also have to be true - that if you sided with the templars, Meredith wouldn't go red-lyrium-crazy (the most awesome boss battle by far). But DA:I and the remaining overall plot of the Dragon Age saga relies on understanding just how crazy red lyrium is. So if you made the choice to side with templars and the red lyrium boss battle didn't happen, you'd find out Meredith's sword is corrupted and she died... another way? Or something else happened to re-inforce the danger of the red lyrium? It wouldn't balance out.
In the end the main point is that the system is what the system is and both sides are right/wrong equally. Siding with one side isn't going to absolve anybody. Suddenly choosing to side with mages or templars isn't going to suddenly justify or make innocent that side.