While some of what you say does highlight one issue I don't like (AI taking over your taunted character is bull, I'd at least like it so that you still control your character, but any attacks can only be performed on the enemy that holds the taunt), however there is one mistake you're making in your summary...
Incarnates don't lose taunt. They simply don't get access to their taunt on their spawn round in which they're summoned. Their next round they do have it. I would have to pretty much agree with this decision. Previously, Taunt was nowhere near as effective as it should be due to the point that by the time physical shields are down, Taunt really isn't much of an issue anymore since at that point you go into full physical DPS mode and wipe the field. Allowing taunt on the summon round would be way overpowered. Dropping an incarnate with a ton of armor into the mix with a guaranteed taunt would be game breaking because it'd basically give your team a free risk free combat round.
Case in point... if I have a summoner in my party with a high enough initiative that he's guaranteed to go first when combat starts, I initiate dialog with a different toon. Switch focus to a toon outside of dialog, teleport all potential enemy combatants to a centralized location, go back to the dialog toon and initiate the combat, then with my summoner who's guaranteed to go first just drops an incarnate champion and taunts immediately. Granting your whole party a free risk free round of combat. That's WAY too OP.
I get that there's already an over abundance of "cheese tactics" in the game. But there doesn't need to be more. Especially when the point of the patch was to create a class/skill balance in an attempt to move away from the "all physical damage builds ruling them all" mechanic.