@malsabku: Please let us distinguish between sans-serif and serif fonts on one hand, and monospace on the other hand.
For sans-serif and serif I know that Arabic speaking users prefer Noto over DejaVu, and currently — as a result of this long thread — there is an arrangement in place for supporting Noto for Arabic. Unfortunately that arrangement was broken for the snaps (including the FF snap). But with the changes I have in mind now we will make Noto truly become the default also for Arabic and also for the snaps.
For monospace: When I said that DejaVu Sans Mono is better, I was specifically talking about the rendering of Arabic scripts in certain terminals, most importantly gnome-terminal at the moment. I don’t speak Arabic myself, and consequently have no own opinion on what looks better, so I defer to this bug report and this discourse thread.