Assasin Multihit

Multihit have higher spell multiplier that spin attack according to help section but I tested it with friend in a duel and after multiple tests spin almost always did more damage
Is that something that happen cuz of elemental defense or its just a bug can someone explain me cuz for now thats make it kinda useless if its cost more mana have less damage and cast slower
(Im not asking for assasin buff dont kill me plz)

 

It could be a couple things. First off the help section for classes is mostly outdated and not very reliable. Also, if you have any spell damage boosts/reductions, that will also significantly change results (% spell damage affects spin attack more while raw spell damage affects multihits more). As you mentioned, elemental defense is always a factor, especially if water defense is included, as multihits has a split water/thunder damage bonus, and spin attack is only thunder. Also, in my experience (might be a bug or just me being delusional) I've found that attack speed has a noticeable difference on spin attack's damage; the higher attack speed, the greater damage. Again, there's as BIG chance this is not true at all but it's just from what I remember. In terms of efficiency, I'm going to have to agree with you about spin attack<multihits as would most people. I do think that the damage should usually be a bit higher with multihits, but with spin attack's lower mana cost as well as its greater AOE/stun/blind/debuff immunity, as opposed to only multihits' knockback, it's usually a better idea to just stick with spin attack. However, multihits does come in handy in high level areas like molten heights and where you can displace your enemies into various hazards. Hope this somewhat answers your question.

Also:

Oh now your in for it boi