I have come to believe, as I once had before taking the time to listen to Loghain, that many of us have our views of Loghain skewed by Alistair's comments at Flemeth's hut after Ostagar. I mean Alistair thinks Loghain wants the throne, and lays all the blame on Loghain.
It also doesn't help that Loghain pretty much puts a bounty on our heads from that moment on, and the soldiers left behind in Lothering made a very poor impression.
But bear in mind, Loghain had been actively arguing with Cailan for days, not only on Orlesian support but also on Cailan being on the battlefield. Cailan was getting really annoyed that Loghain told him point blank that he shouldn't be playing hero and that it was too dangerous. The soldiers, both Cailan's guard and Loghain's, each acknowledge this fact.
Loghain also has been confirmed by the lead writer that he wasn't planning on abandoning Cailan.
Loghain is a poor public speaker and lousy politican, and came across as if he were giving orders to the bannorn, which likely rubbed them the wrong way. Add in the fact that even the soldiers at Ostagar are having a very hard time getting over the fact that he was a commoner who had been elevated to one of the highest of noblemen in Ferelden, one of only two teyrns in the country. If it rubbed common soldiers the wrong way, you can bet every sovereign you can make in the game that it most certainly bothered a lot of nobles who had been nobles for generations.
The codex also makes it clear that while some banns, like Teagan, were in it for altruistic reasons to oppose Loghain, most were trying to take advantage of the power vacuum.
The gossipers makes it very clear that Loghain wins nearly every battle, and those he loses are the ones the Warden participates in or are in areas that get swallowed up by the blight by the lords who successfully won, but no longer had the strength to fight the darkspawn. And by the time the landsmeet occurs, Loghain has pretty much won the civil war, but people were now worried about the increasingly obvious darkspawn threat, and the fact that Ferelden no longer really had the strength to fight a blight. This can't all be blamed on Loghain because he only fought those who, from the scene with Howe on how the nobles were gathering there forces to fight each other instead of the darkspawn (the scene where he hires Zevran,) because every noble who decided to fight in the civil war share in the blame as well.
Poisoning Eamon by hiring a blood mage, selling elves into slavery, and so on I won't bother trying to defend because he's clearly guilty in those situations, but I no longer can simply hate or blame Loghain for every single bad thing that happens in the game, as far as Ferelden is concerned.