I picked all of them. None of the bosses or midbosses gave me any particular trouble. Actually, I found early on (2nd-3rdish playtyhrough) that all enemies in the game have terribad AI, which means they are easily looped. For example, Dark Lord Ganondorf has this horrible method of RNG which determines what he'll do. Approach him so he stops moving, back up, then see if he charges at you. If not, repeat the method. I guarantee you will finish him with no effort.
Darknuts...you can literally run around them pressing B/swinging the Wiimote and you will land one hit in, then follow up with 2 more (they block the final slash of Link's 4 hit combo). No trouble.
Deku Toad...can't say anything about him.
Horseback Ganondorf - lulz.
All forms of Zant were a joke + Phantom Zant minibosses.
Argorok really just relies on your ability to switch between the floaty peahats. Nothing to it, really.
Death Sword really makes me angry. He had one of the best miniboss rooms, but it was insanely easy to loop him. Come on, a silly arrow can make you visible and in a rage? Poor display, buddy!