I just started a Tactician playthrough and I completely agree. I use a few more buff and debuff spells, but most fights are boringly easy. The complicated ones are the ones where you are trying to save someone else, just as it was at standard difficulty, but that is not really related to the difficulty setting, but the nature of the fight. Still in Act I, so it might be better later on, but I highly doubt it as I am a completetionist, so I tend to be at at very high level when I reach new areas, so maybe the game should have some kind of scaling system, where the world scales up with your level to a certain degree.