Just wondering. During the champion select, what makes a team say, "We should have Fiddle jungling." Also, who takes mid?

In my personal opinion the times where a mage jungler comes in handy is when you have something like a Talon, GP, Pantheon etc mid to maybe counter their Morgana or tough ap mid. This would allow you to still stick a bruiser type up top and have a good team comp with your ap carry in the jungle. Im sure there a lot more examples like times they make a good counterpick and such but I would like to hear some more opinions on this as well.

2 ap, 2 ad, 1 support, you seek a balance based on who is top lane