Left-clicking will make him swing for damage, and right-clicking will stop you immediately for the stun.
Definitely disagree with this. Opinions are opinions, but I think the game is full of some great skins. Jack the Reaper Thanatos, Digi-Ymir, Swagni, Triumph and Agni, Convention Artemis, Slaughterhouse Chaac, Lord Slashington III Fenrir, All for One Freya, Classic Hades, Grim Wraith Hades, Solstice Hel, Infinity Wave He Bo, Derpules, Jandroid, Riftshaker Janus, Bass Drop Janus, Infiltrator Loki, Scarlet Coven Isis, Trophy Hunter Kali, Aphra Cadabra Aphrodite, Orbital Strike Rama... The list goes on and on...
If you're having difficulty with this, I assure you, it'll come with time. There are very few, if any, skills in the game that I think are too difficult to hit and need redesigning. Eventually you'll get the hang of them after using the character enough.
Haven't tried out Fafnir yet, but he looks pretty cool. Athena's a super fun Guardian, so I'd definitely recommend her. One of my favorites in that class.