This is not a mobile device problem or an iOS problem. This is a competence problem with your designers. The role of a UX designer is not to produce a portrait-only, default-font-size-only pixel-perfect picture on three popular phone screen sizes, and throw it over the fence for developers to develop and not ask questions. Designers must ask, what if the user prefers landscape mode? What if their fonts need to be larger for accessibility reasons? What if they are on an odd sized phone, or even one we haven't even seen yet?