Yes, you have to keep re-assigning the target.

It is very annoying when you're chasing, you can't cast anything unless you can make up the difference since you stop to cast and then don't start to move until you click again.

Yes, whenever you use an ability your demigod will stop in his tracks once it is completed. You then need to tell him to attack that demigod again. Its not that they start attacking the minions, it is just them defending themselves whenever something hositle is nearby since they are "idle".

In other words Demigods can only be told and remember one thing at a time. They don't upon completion revert to a previous command. Attack a Demigod and Use an ability are two different commands. Hope this made sense.

They need to make it a toggle...I think it's pretty rare I would want to shoot a creep/minion with my 1300pt Fireball.

Yeah but that creep/minion isn't gonna mess you with anymore is he.

But I agree a toggle would be nice, don't think I have ever actaully wanted to target a minion or creep. Just move close and let autoattack go crazy works much better. ie. Minion could die before you get there, so you stop. Or AoE the little bastards which again isn't targeting them.