Word of mouth is more important for movies but that only affects it after the first days so that even word of mouth doesn't affect the most important days that much. So, if people will tell their friends not to see it, the legs will be bad (% wise compared to first weekend). If people will like it the legs will be probably decent but first weekend numbers will be good regardless of what people who saw it will say.
Important is if people liked the trailers and other marketing before release and most liked the trailers. They were really good, the music in the trailers did a great job as well.
I think that was also a reason why Deadpool started already decent even with almost nobody knowing him before. The marketing before release was something many people really liked. It caught their attention and interest so that they went to the cinema.
