A point character is what you want to start with.
People start with Bella point, filia point, Anybody point.
However the composition comes into play when you're picking 2 or 3 character(obviously). anyone could certainly be anchor, but you have to look at the strengths and weaknesses of the character.
For example. Fortune is mainly a point character. Why?
Her assist is Meh compared to some of the cast.
She has very good mobility and she can do damage.
Most importantly she builds meter like crazy for the rest of her team.
For this reason alone people pick fortune point.
You also have to take into account of the anchor's main purpose.
The anchor must have good comeback potiential.
Can hit hard when the times beckons for it.
Can operate extremely well.
For this reason most people do not pick val ANchor cause she is weak alone and does well with assist. Same goes for Squigly in which she needs meter and charge to be scary.
@Man-In-Crowd-4