Auto target works on Ex Hard, if I remember right. It's always an option, unless I'm forgetting things... Besides, not using auto target can be kind of fun, too. Not so much if you're using rifles in a non-sniping mode, but for the other guns it's neat. Especially the Ultima Weapon (shameless plug, again) with it's feather-light weight and sublime accuracy - even with the EXP-doubling Lucky S-barrel.
Hmm, I really ought to play this game some more. Seems there's still more stuff to get, and I'm intent on doing a complete play-through in first-person view.
Is there a handy list of how to get the 'ultimate' weapon of each type?