((The initial quest lines could provide the opportunity to familiarize a new player to the basic mechanics of the game.))
If by basic mechanics you mean the concepts of killing things to get experience and drops, and doing quests to get experience and rewards - this may well work.
If by basic mechanics you mean how chat channels work, how to move, how to adjust the camera angle, how to attack, what a quickbar is, what a skill is and whether skills are used by clicking icons, etc. etc a new player can get easily overwhelmed especially if they are hit with guild and group invitations and chat whispers before they even know *how* to respond much less what all of this means.
Even I, who has played as many MMOs as most, prefer 15 or 30 minutes of peace in a new one as I figure out all of the options, keybinds, audio and video settings and the like. So I see no reason at all not to give new players an optional tutorial on the *really* basic mechanics and a chance to customize keybinds and the like to their preferences.