the apostroph is placed if it describes the belonging of somebody. steve's car. but if you do it in plural, you do it without apostrophe: alot of steves.

so dice's world would be a world that belongs to one die, or as modern english says: dice.

if you do pkural, it should be dices world. however, i agree that dice world sounds better. its like world of dice (welt der würfel, welt des würfels, würfels welt in deinem fall) and thus, id say you should use that.

and while im not an expert my wife who studied anglistics agrees. and i trust ehr on that